Hubble Space Telescope

# Hubble Space Telescope

The **Hubble Space Telescope** (**HST** or **Hubble**) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned as a vital research tool and as a public relations boon for astronomy. The Hubble Space Telescope is named after astronomer Edwin Hubble and is one of NASA 's Great Observatories. The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center (GSFC) controls the spacecraft.[^8]

Hubble features a 2.4 m (7 ft 10 in) mirror, and its five main instruments observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. Hubble's orbit outside the distortion of Earth's atmosphere allows it to capture extremely high-resolution images with substantially lower background light than ground-based telescopes. It has recorded some of the most detailed visible light images, allowing a deep view into space. Many Hubble observations have led to breakthroughs in astrophysics, such as determining the rate of expansion of the universe.

The Hubble Space Telescope was funded and built in the 1970s by NASA with contributions from the European Space Agency. Its intended launch was in 1983, but the project was beset by technical delays, budget problems, and the 1986 *Challenger* disaster. Hubble was launched on STS-31 in 1990, but its main mirror had been ground incorrectly, resulting in spherical aberration that compromised the telescope's capabilities. The optics were corrected to their intended quality by a servicing mission, STS-61, in 1993.

Hubble is the only telescope designed to be maintained in space by astronauts. Five Space Shuttle missions repaired, upgraded, and replaced systems on the telescope, including all five of the main instruments. The fifth mission was initially canceled on safety grounds following the *Columbia* disaster (2003), but after NASA administrator Michael D. Griffin approved it, the servicing mission was completed in 2009. Hubble completed 30 years of operation in April 2020 [^1] and is predicted to last until 2030 to 2040.[^4]

Hubble is the visible light telescope in NASA's Great Observatories program; other parts of the spectrum are covered by the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope (which covers the infrared bands).[^9] The mid-IR-to-visible band successor to the Hubble telescope is the James Webb Space Telescope (JWST), which was launched on December 25, 2021, with the Nancy Grace Roman Space Telescope due to follow in 2026.[^10] [^11] [^12]

## Concept, design and aim

### Proposals and precursors

In 1923 Hermann Oberth, considered a father of modern rocketry along with Robert H. Goddard and Konstantin Tsiolkovsky, published **Die Rakete zu den Planetenräumen** ("The Rocket into Planetary Space"), which mentioned how a telescope could be propelled into Earth orbit by a rocket.[^13]

Lyman Spitzer played a major role in the birth of the Hubble Space Telescope project.

The history of the Hubble Space Telescope can be traced to 1946, to astronomer Lyman Spitzer 's paper "Astronomical advantages of an extraterrestrial observatory".[^14] In it, he discussed the two main advantages that a space-based observatory would have over ground-based telescopes. First, the angular resolution (the smallest separation at which objects can be clearly distinguished) would be limited only by diffraction, rather than by the turbulence in the atmosphere, which causes stars to twinkle, known to astronomers as seeing. At that time ground-based telescopes were limited to resolutions of 0.5–1.0 arcseconds, compared to a theoretical diffraction-limited resolution of about 0.05 arcsec for an optical telescope with a mirror 2.5 m (8 ft 2 in) in diameter. Second, a space-based telescope could observe infrared and ultraviolet light, which are strongly absorbed by the atmosphere of Earth.[^14]

Spitzer devoted much of his career to pushing for the development of a space telescope.[^15] In 1962, a report by the U.S. National Academy of Sciences recommended development of a space telescope as part of the space program, and in 1965, Spitzer was appointed as head of a committee given the task of defining scientific objectives for a large space telescope.[^16]

Nancy Grace Roman with a model of the Large Space Telescope that was eventually developed as the Hubble Space Telescope. While listed as a 1966 photo, this design was not the standard until the mid-1970s.

Also crucial was the work of Nancy Grace Roman, the "Mother of Hubble".[^17] Well before it became an official NASA project, she gave public lectures touting the scientific value of the telescope. After it was approved, she became the program scientist, setting up the steering committee in charge of making astronomer needs feasible to implement [^18] and writing testimony to Congress throughout the 1970s to advocate continued funding of the telescope.[^19] Her work as project scientist helped set the standards for NASA's operation of large scientific projects.[^20]

American astronomer Edwin P. Hubble (pictured in 1931), for whom the telescope is named.

Space-based astronomy had begun on a very small scale following World War II, as scientists made use of developments that had taken place in rocket technology. The first ultraviolet spectrum of the Sun was obtained in 1946,[^21] and NASA launched the Orbiting Solar Observatory (OSO) to obtain UV, X-ray, and gamma-ray spectra in 1962.[^22] An orbiting solar telescope was launched in 1962 by the United Kingdom as part of the Ariel programme, and in 1966 NASA launched the first Orbiting Astronomical Observatory (OAO) mission. OAO-1's battery failed after three days, terminating the mission. It was followed by Orbiting Astronomical Observatory 2 (OAO-2), which carried out ultraviolet observations of stars and galaxies from its launch in 1968 until 1972, well beyond its original planned lifetime of one year.[^23]

The OSO and OAO missions demonstrated the important role space-based observations could play in astronomy. In 1968, NASA developed firm plans for a space-based reflecting telescope with a mirror 3 m (9.8 ft) in diameter, known provisionally as the Large Orbiting Telescope or Large Space Telescope (LST), with a launch slated for 1979. These plans emphasized the need for crewed maintenance missions to the telescope to ensure such a costly program had a lengthy working life, and the concurrent development of plans for the reusable Space Shuttle indicated that the technology to allow this was soon to become available.[^24]

### Quest for funding

The continuing success of the OAO program encouraged increasingly strong consensus within the astronomical community that the LST should be a major goal. In 1970, NASA established two committees, one to plan the engineering side of the space telescope project, and the other to determine the scientific goals of the mission. Once these had been established, the next hurdle for NASA was to obtain funding for the instrument, which would be far more costly than any Earth-based telescope. The U.S. Congress questioned many aspects of the proposed budget for the telescope and forced cuts in the budget for the planning stages, which at the time consisted of very detailed studies of potential instruments and hardware for the telescope. In 1974, public spending cuts led to Congress deleting all funding for the telescope project.[^25]

Astronaut Owen Garriott working next to Skylab's crewed solar space observatory, 1973

In 1977, then NASA Administrator James C. Fletcher proposed a token $5 million for Hubble in NASA's budget. Then NASA Associate Administrator for Space Science, Noel Hinners, instead cut all funding for Hubble, gambling that this would galvanize the scientific community into fighting for full funding. As Hinners recalls:[^26]

> It was clear that year that we weren't going to be able to get a full-up start. There was some opposition on \[Capitol\] Hill to getting a new start on \[Hubble\]. It was driven, in large part as I recall, by the budget situation. Jim Fletcher proposed that we put in five million as a placeholder. I didn't like that idea. It was, in today's vernacular, a "sop" to the astronomy community. "There's something in there, so all is well".
> 
> I figured in my own little head that to get that community energized we'd be better off zeroing it out. Then they would say, "Whoa, we're in deep trouble", and it would marshal the troops. So I advocated that we not put anything in. I don't remember any of the detailed discussions or whether there were any, but Jim went along with that so we zeroed it out. It had, from my perspective, the desired impact of stimulating the astronomy community to renew their efforts on the lobbying front. While I like to think in hindsight it was a brilliant political move, I'm not sure I thought it through all that well. It was something that was spur of the moment.
> 
> \[...\] five million would let them think that all is well anyway, but it's not. So let's give them a message. My own thinking, get them stimulated to get into action. Zeroing it out would certainly give that message. I think it was as simple as that. Didn't talk to anybody else about doing it first, just, "Let's go do that". Voila, it worked. Don't know whether I'd do that again.

The political ploy worked. In response to Hubble being zeroed out of NASA's budget, a nationwide lobbying effort was coordinated among astronomers. Many astronomers met congressmen and senators in person, and large-scale letter-writing campaigns were organized. The National Academy of Sciences published a report emphasizing the need for a space telescope, and eventually, the Senate agreed to half the budget that had originally been approved by Congress.[^27]

The funding issues led to a reduction in the scale of the project, with the proposed mirror diameter reduced from 3 m to 2.4 m, both to cut costs [^28] and to allow a more compact and effective configuration for the telescope hardware. A proposed precursor 1.5 m (4 ft 11 in) space telescope to test the systems to be used on the main satellite was dropped, and budgetary concerns also prompted collaboration with the European Space Agency (ESA). ESA agreed to provide funding and supply one of the first generation instruments for the telescope, as well as the solar cells that would power it, and staff to work on the telescope in the United States, in return for European astronomers being guaranteed at least 15% of the observing time on the telescope.[^29] Congress eventually approved funding of $36 million for 1978, and the design of the LST began in earnest, aiming for a launch date of 1983.[^27] In 1983, the telescope was named after Edwin Hubble,[^30] who confirmed one of the greatest scientific discoveries of the 20th century, made by Georges Lemaître, that the universe is expanding.[^31]

### Construction and engineering

Grinding of Hubble's primary mirror at Perkin-Elmer, March 1979

Once the Space Telescope project had been given the go-ahead, work on the program was divided among many institutions. Marshall Space Flight Center (MSFC) was given responsibility for the design, development, and construction of the telescope, while Goddard Space Flight Center was given overall control of the scientific instruments and ground-control center for the mission.[^32] MSFC commissioned the optics company Perkin-Elmer to design and build the optical telescope assembly (OTA) and Fine Guidance Sensors for the space telescope. Lockheed was commissioned to construct and integrate the spacecraft in which the telescope would be housed.[^33]

### Optical telescope assembly

Optically, the HST is a Cassegrain reflector of Ritchey–Chrétien design, as are most large professional telescopes. This design, with two hyperbolic mirrors, is known for good imaging performance over a wide field of view, with the disadvantage that the mirrors have shapes that are hard to fabricate and test. The mirror and optical systems of the telescope determine the final performance, and they were designed to exacting specifications. Optical telescopes typically have mirrors polished to an accuracy of about a tenth of the wavelength of visible light, but the Space Telescope was to be used for observations from the visible through the ultraviolet (shorter wavelengths) and was specified to be diffraction limited to take full advantage of the space environment. Therefore, its mirror needed to be polished to an accuracy of 10 nanometers, or about 1/65 of the wavelength of red light.[^34] On the long wavelength end, the OTA was not designed with optimum infrared performance in mind, e.g. the mirrors are kept at stable (and warm, about 15°C) temperatures by heaters. This limits Hubble's performance as an infrared telescope.[^35]

The backup mirror, by Kodak; its inner support structure can be seen because it is not coated with a reflective surface.

Perkin-Elmer (PE) intended to use custom-built and extremely sophisticated computer-controlled polishing machines to grind the mirror to the required shape.[^33] However, in case their cutting-edge technology ran into difficulties, NASA demanded that PE sub-contract to Kodak to construct a back-up mirror using traditional mirror-polishing techniques.[^36] (The team of Kodak and Itek also bid on the original mirror polishing work. Their bid called for the two companies to double-check each other's work, which would have almost certainly caught the polishing error that later caused problems.) [^37] The Kodak mirror is now on permanent display at the National Air and Space Museum.[^38] [^39] An Itek mirror built as part of the effort is now used in the 2.4 m telescope at the Magdalena Ridge Observatory.[^40]

Construction of the Perkin-Elmer mirror began in 1979, starting with a blank manufactured by Corning from their ultra-low expansion glass. To keep the mirror's weight to a minimum it consisted of top and bottom plates, each 25 mm (0.98 in) thick, sandwiching a honeycomb lattice. Perkin-Elmer simulated microgravity by supporting the mirror from the back with 130 rods that exerted varying amounts of force.[^41] This ensured the mirror's final shape would be correct and to specification when deployed. Mirror polishing continued until May 1981. NASA reports at the time questioned Perkin-Elmer's managerial structure, and the polishing began to slip behind schedule and over budget. To save money, NASA halted work on the back-up mirror and moved the launch date of the telescope to October 1984.[^42] The mirror was completed by the end of 1981; it was washed using 9,100 L (2,000 imp gal; 2,400 US gal) of hot, deionized water and then received a reflective coating of 65‑nm‑thick aluminum and a protective coating of 25‑nm‑thick magnesium fluoride.[^35] [^43]

The OTA, metering truss, and secondary baffle are visible in this image of Hubble during early construction.

Doubts continued to be expressed about Perkin-Elmer's competence on a project of this importance, as their budget and timescale for producing the rest of the OTA continued to inflate. In response to a schedule described as "unsettled and changing daily", NASA postponed the launch date of the telescope until April 1985. Perkin-Elmer's schedules continued to slip at a rate of about one month per quarter, and at times delays reached one day for each day of work. NASA was forced to postpone the launch date until March and then September 1986. By this time, the total project budget had risen to $1.175 billion.[^44]

### Spacecraft systems

The spacecraft in which the telescope and instruments were to be housed was another major engineering challenge. It would have to withstand frequent passages from direct sunlight into the darkness of Earth's shadow, which would cause major changes in temperature, while being stable enough to allow extremely accurate pointing of the telescope. A shroud of multi-layer insulation keeps the temperature within the telescope stable and surrounds a light aluminum shell in which the telescope and instruments sit. Within the shell, a graphite-epoxy frame keeps the working parts of the telescope firmly aligned.[^45] Because graphite composites are hygroscopic, there was a risk that water vapor absorbed by the truss while in Lockheed's clean room would later be expressed in the vacuum of space; resulting in the telescope's instruments being covered by ice. To reduce that risk, a nitrogen gas purge was performed before launching the telescope into space.[^46]

As well as electrical power systems, the **Pointing Control System** controls HST orientation using five types of sensors (magnetic sensors, optical sensors, and six gyroscopes) and two types of actuators (reaction wheels and magnetic torquers).[^47]

While construction of the spacecraft in which the telescope and instruments would be housed proceeded somewhat more smoothly than the construction of the OTA, Lockheed experienced some budget and schedule slippage, and by the summer 1985, construction of the spacecraft was 30% over budget and three months behind schedule. An MSFC report said Lockheed tended to rely on NASA directions rather than take their own initiative in the construction.[^48]

### Computer systems and data processing

DF-224 in Hubble, before it was replaced in 1999

The two initial, primary computers on the HST were the 1.25 MHz DF-224 system, built by Rockwell Autonetics, which contained three redundant CPUs, and two redundant NSSC-1 (NASA Standard Spacecraft Computer, Model 1) systems, developed by Westinghouse and GSFC using diode–transistor logic (DTL). A co-processor for the DF-224 was added during Servicing Mission 1 in 1993, which consisted of two redundant strings of an Intel-based 80386 processor with an 80387 math co-processor.[^49] The DF-224 and its 386 co-processor were replaced by a 25 MHz Intel-based 80486 processor system during Servicing Mission 3A in 1999.[^50] The new computer is 20 times faster, with six times more memory, than the DF-224 it replaced. It increases throughput by moving some computing tasks from the ground to the spacecraft and saves money by allowing the use of modern programming languages.[^51]

Additionally, some of the science instruments and components had their own embedded microprocessor-based control systems. The MATs (Multiple Access Transponder) components, MAT-1 and MAT-2, use Hughes Aircraft CDP1802CD microprocessors.[^52] The Wide Field and Planetary Camera (WFPC) also used an RCA 1802 microprocessor (or possibly the older 1801 version).[^53] The WFPC-1 was replaced by the WFPC-2 during Servicing Mission 1 in 1993, which was then replaced by the Wide Field Camera 3 (WFC3) during Servicing Mission 4 in 2009. The upgrade extended Hubble's capability of seeing deeper into the universe and providing images in three broad regions of the spectrum.[^54] [^55]

### Initial instruments

Exploded view of the Hubble Space Telescope

When launched, the HST carried five scientific instruments: the Wide Field and Planetary Camera (WF/PC), Goddard High Resolution Spectrograph (GHRS), High Speed Photometer (HSP), Faint Object Camera (FOC) and the Faint Object Spectrograph (FOS). WF/PC used a radial instrument bay, and the other four instruments were each installed in an axial instrument bay.[^56]

WF/PC was a high-resolution imaging device primarily intended for optical observations. It was built by NASA's Jet Propulsion Laboratory, and incorporated a set of 48 filters isolating spectral lines of particular astrophysical interest. The instrument contained eight charge-coupled device (CCD) chips divided between two cameras, each using four CCDs. Each CCD has a resolution of 0.64 megapixels.[^57] The wide field camera (WFC) covered a large angular field at the expense of resolution, while the planetary camera (PC) took images at a longer effective focal length than the WF chips, giving it a greater magnification.[^56]

The Goddard High Resolution Spectrograph (GHRS) was a spectrograph designed to operate in the ultraviolet. It was built by the Goddard Space Flight Center and could achieve a spectral resolution of 90,000.[^58] Also optimized for ultraviolet observations were the FOC and FOS, which were capable of the highest spatial resolution of any instruments on Hubble. Rather than CCDs, these three instruments used photon -counting digicons as their detectors. The FOC was constructed by ESA, while the University of California, San Diego, and Martin Marietta Corporation built the FOS.[^56]

The final instrument was the HSP, designed and built at the University of Wisconsin–Madison. It was optimized for visible and ultraviolet light observations of variable stars and other astronomical objects varying in brightness. It could take up to 100,000 measurements per second with a photometric accuracy of about 2% or better.[^59]

HST's guidance system can also be used as a scientific instrument. Its three Fine Guidance Sensors (FGS) are primarily used to keep the telescope accurately pointed during an observation, but can also be used to carry out extremely accurate astrometry; measurements accurate to within 0.0003 arcseconds have been achieved.[^60]

### Ground support

Hubble Control Center at Goddard Space Flight Center, 1999

The Space Telescope Science Institute (STScI) is responsible for the scientific operation of the telescope and the delivery of data products to astronomers. STScI is operated by the Association of Universities for Research in Astronomy (AURA) and is physically located in Baltimore, Maryland on the Homewood campus of Johns Hopkins University, one of the 39 U.S. universities and seven international affiliates that make up the AURA consortium. STScI was established in 1981 [^61] [^62] after something of a power struggle between NASA and the scientific community at large. NASA had wanted to keep this function in-house, but scientists wanted it to be based in an academic establishment.[^63] [^64] The Space Telescope European Coordinating Facility (ST-ECF), established at Garching bei München near Munich in 1984, provided similar support for European astronomers until 2011, when these activities were moved to the European Space Astronomy Centre.[^65]

One complex task that falls to STScI is scheduling observations for the telescope.[^66] Hubble is in a low-Earth orbit to enable servicing missions, which results in most astronomical targets being occulted by the Earth for slightly less than half of each orbit. Observations cannot take place when the telescope passes through the South Atlantic Anomaly due to elevated radiation levels, and there are also sizable exclusion zones around the Sun (precluding observations of Mercury), Moon and Earth. The solar avoidance angle is about 50°, to keep sunlight from illuminating any part of the OTA. Earth and Moon avoidance keeps bright light out of the FGSs, and keeps scattered light from entering the instruments. If the FGSs are turned off, the Moon and Earth can be observed. Earth observations were used very early in the program to generate flat-fields for the WFPC1 instrument. There is a so-called continuous viewing zone (CVZ), within roughly 24° of Hubble's orbital poles, in which targets are not occulted for long periods.[^67] [^68] [^69]

[^1]: "Hubble Marks 30 Years in Space with Tapestry of Blazing Starbirth". *HubbleSite.org*. Space Telescope Science Institute. April 24, 2020. Archived from the original on May 10, 2020. Retrieved April 24, 2020.

[^2]: "Hubble Essentials: Quick Facts". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on July 6, 2016.

[^3]: Ryba, Jeanne. "STS-31". NASA. Archived from the original on May 7, 2017. Retrieved May 7, 2017. This article incorporates text from this source, which is in the public domain.

[^4]: Harwood, William (May 30, 2013). "Four years after final service call, Hubble Space Telescope going strong". *CBS News*. Archived from the original on October 30, 2019. Retrieved June 3, 2013.

[^5]: "Hubble Space Telescope – Orbit". Heavens Above. August 15, 2018. Archived from the original on August 17, 2018. Retrieved August 16, 2018.

[^6]: Nelson, Buddy (2009). "Hubble Space Telescope: Servicing Mission 4 Media Reference Guide" (PDF). NASA/Lockheed Martin. pp. 1–5. Archived (PDF) from the original on August 27, 2011. Retrieved May 31, 2018.

[^7]: NASA. "FAQ for Scientists Webb Telescope". Archived from the original on February 10, 2022. Retrieved February 15, 2022.

[^8]: "Hubble Essentials". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on March 3, 2016. Retrieved March 3, 2016. This article incorporates text from this source, which is in the public domain.

[^9]: Canright, Shelley. "NASA's Great Observatories". NASA. Archived from the original on June 20, 2015. Retrieved April 26, 2008. This article incorporates text from this source, which is in the public domain.

[^10]: "NASA Announces New James Webb Space Telescope Target Launch Date". NASA. July 16, 2020. Archived from the original on July 18, 2020. Retrieved September 10, 2020. This article incorporates text from this source, which is in the public domain.

[^11]: Overbye, Dennis (July 16, 2020). "NASA Delays James Webb Telescope Launch Date, Again – The universe will have to wait a little longer". *The New York Times*. Archived from the original on December 14, 2021. Retrieved July 17, 2020.

[^12]: "Hubble successor given mid-December launch date". *BBC News*. September 9, 2021. Archived from the original on September 9, 2021. Retrieved September 10, 2021.

[^13]: Oberth, Hermann (1923). *Die Rakete zu den Planetenräumen* (in German). R. Oldenbourg-Verlay. p. 85.

[^14]: Spitzer, Lyman Jr., "Report to Project Rand: Astronomical Advantages of an Extra-Terrestrial Observatory", reprinted in *NASA SP-2001-4407: Exploring the Unknown* Archived January 20, 2017, at the Wayback Machine, Chapter 3, Document III-1, p. 546.

[^15]: "Celebrating Lyman Spitzer, the father of PPPL and the Hubble Space Telescope". *Office of the Dean for Research*. Archived from the original on December 7, 2021. Retrieved December 4, 2021.

[^16]: "About Lyman Spitzer, Jr". Caltech. Archived from the original on March 27, 2008. Retrieved April 26, 2008.

[^17]: Smith, Yvette (May 15, 2020). "Nancy Grace Roman: The Mother of Hubble". *NASA*. Archived from the original on December 7, 2021. Retrieved December 4, 2021.

[^18]: "Explorer 1 | Stories | Nancy Grace Roman". *explorer1.jpl.nasa.gov*. Archived from the original on May 31, 2022. Retrieved December 4, 2021.

[^19]: Roman, Nancy Grace (2019). "Nancy Grace Roman and the Dawn of Space Astronomy". *Annual Review of Astronomy and Astrophysics*. **57**: 1–34. Bibcode:2019ARA&A..57....1R. doi:10.1146/annurev-astro-091918-104446.

[^20]: Williams, Robert (October 1, 2018). *Hubble Deep Field and the Distant Universe*. Bristol, UK: IOP Publishing. pp. 2–9. ISBN 978-0-7503-1756-6. Archived from the original on June 5, 2020.

[^21]: Baum, W. A.; Johnson, F. S.; Oberly, J. J.; Rockwood, C. C.; et al. (November 1946). "Solar Ultraviolet Spectrum to 88 Kilometers". *Physical Review*. **70** (9–10): 781–782. Bibcode:1946PhRv...70..781B. doi:10.1103/PhysRev.70.781.

[^22]: "The First Orbiting Solar Observatory". *heasarc.gsfc.nasa.gov*. NASA Goddard Space Flight Center. June 26, 2003. Archived from the original on May 3, 2019. Retrieved September 25, 2011. This article incorporates text from this source, which is in the public domain.

[^23]: "OAO". NASA. Archived from the original on September 16, 2008. Retrieved April 26, 2008. This article incorporates text from this source, which is in the public domain.

[^24]: Spitzer 1979, p. 32.

[^25]: Spitzer 1979, pp. 33–34.

[^26]: "NASA Headquarters Oral History Project – Noel W. Hinners". *Johnson Space Center History Portal*. NASA. August 19, 2010. Archived from the original on July 15, 2022. Retrieved July 14, 2022.

[^27]: Spitzer 1979, p. 34.

[^28]: Andersen, Geoff (2007). *The telescope: its history, technology, and future*. Princeton University Press. p. 116. ISBN 978-0-691-12979-2.

[^29]: "Memorandum of Understanding Between The European Space Agency and The United States National Aeronautics and Space Administration", reprinted in *NASA SP-2001-4407: Exploring the Unknown* Archived January 20, 2017, at the Wayback Machine Chapter 3, Document III-29, p. 671.

[^30]: Okolski, Gabriel. "A Chronology of the Hubble Space Telescope". NASA. Archived from the original on June 27, 2008. Retrieved April 26, 2008. This article incorporates text from this source, which is in the public domain.

[^31]: "The Path to Hubble Space Telescope". NASA. Archived from the original on May 24, 2008. Retrieved April 26, 2008. This article incorporates text from this source, which is in the public domain.

[^32]: Dunar & Waring 1999, pp. 487–488.

[^33]: Dunar & Waring 1999, p. 489.

[^34]: Waldrop, M. M. (August 17, 1990). "Hubble: The Case of the Single-Point Failure". *Science Magazine*. **249** (4970): 735–736. Bibcode:1990Sci...249..735W. doi:10.1126/science.249.4970.735. PMID 17756776.

[^35]: Robberto, M.; Sivaramakrishnan, A.; Bacinski, J. J.; Calzetti, Daniele; Krist, J. E.; MacKenty, J. W.; Piquero, J.; Stiavelli, M. (2000). Breckinridge, James B.; Jakobsen, Peter (eds.). "The Performance of HST as an Infrared Telescope". *Proc. SPIE*. UV, Optical, and IR Space Telescopes and Instruments. **4013**: 386–393. Bibcode:2000SPIE.4013..386R. CiteSeerX 10.1.1.358.1298. doi:10.1117/12.394037. S2CID 14992130. This article incorporates text from this source, which is in the public domain.

[^36]: Allen et al. 1990, pp. 3–4.

[^37]: "Losing Bid Offered Two Tests on Hubble". *The New York Times*. Associated Press. July 28, 1990. Archived from the original on February 4, 2009. Retrieved April 26, 2008.

[^38]: Goddard Space Flight Center (September 21, 2001). "Hubble Space Telescope Stand-in Gets Starring Role" (Press release). NASA. Archived from the original on February 26, 2008. Retrieved April 26, 2008. This article incorporates text from this source, which is in the public domain.

[^39]: "Backup Mirror, Hubble Space Telescope". National Air and Space Museum. Archived from the original on November 2, 2012. Retrieved November 4, 2012.

[^40]: Magdalena Ridge Observatory (January 1, 2008). *2.4m Observatory Technical Note* (PDF) (Technical report). 1.6. p. 2. Archived (PDF) from the original on March 4, 2016. Retrieved January 21, 2013.

[^41]: McCarthy, Daniel J.; Facey, Terence A. (1982). Yoder, Jr., Paul R. (ed.). *Design and fabrication of the NASA 2.4-meter space telescope*. *Proc. SPIE 0330, Optical Systems Engineering II*. Optical Systems Engineering II. Vol. 0330. International Society for Optics and Photonics. pp. 139–143. doi:10.1117/12.934268.

[^42]: Dunar & Waring 1999, p. 496.

[^43]: Ghitelman, David (1987). *The Space Telescope*. New York: Michael Friedman. p. 32. ISBN 978-0-8317-7971-9.

[^44]: Dunar & Waring 1999, p. 504.

[^45]: "Hubble Space Telescope Systems". Goddard Space Flight Center. Archived from the original on March 17, 2003. Retrieved April 26, 2008. This article incorporates text from this source, which is in the public domain.

[^46]: Ghitelman, David (1987) *The Space Telescope,* New York: Michael Friedman Publishing, p. 50.

[^47]: "Hubble Space Telescope Pointing Control System". NASA. December 19, 2017. Archived from the original on February 12, 2019. Retrieved October 24, 2018.

[^48]: Dunar & Waring 1999, p. 508.

[^49]: "Co-Processor" (PDF). NASA Facts. NASA. June 1993. NF-193. Archived (PDF) from the original on July 23, 2012. Retrieved May 16, 2016. This article incorporates text from this source, which is in the public domain.

[^50]: "Hubble Space Telescope Servicing Mission 3A: New Advanced Computer" (PDF). NASA Facts. NASA. 1999. FS-1999-06-009-GSFC. Archived (PDF) from the original on May 9, 2016. Retrieved May 16, 2016.

[^51]: Lockheed Martin Missiles and Space. *Hubble Space Telescope Servicing Mission 3A Media Reference Guide* (PDF) (Technical report). NASA. pp. 5–9 and Section 7.1.1. Archived (PDF) from the original on November 25, 2011. Retrieved April 7, 2022. This article incorporates text from this source, which is in the public domain.

[^52]: Xapsos, M. A.; Stauffer, C.; Jordan, T.; Poivey, C.; Haskins, D. N.; Lum, G.; Pergosky, A. M.; Smith, D. C.; LaBel, K. A. (December 2014). "How Long Can the Hubble Space Telescope Operate Reliably? A Total Dose Perspective" (PDF). *IEEE Transactions on Nuclear Science*. **61** (6): 3356–3362. Bibcode:2014ITNS...61.3356X. doi:10.1109/TNS.2014.2360827. hdl:2060/20160005759. S2CID 1792941. Archived (PDF) from the original on February 27, 2017. Retrieved July 7, 2017. This article incorporates text from this source, which is in the public domain.

[^53]: Afshari, A. (January 1993). "Hubble Space Telescope's Wide Field/Planetary Camera" (PDF). *Shutterbug*. Archived from the original (PDF) on October 6, 2016. This article incorporates text from this source, which is in the public domain.

[^54]: "The 'Camera That Saved Hubble'". *NASA Jet Propulsion Laboratory (JPL)*. Archived from the original on November 27, 2021. Retrieved November 27, 2021.

[^55]: Garner, Rob (August 22, 2016). "Hubble Space Telescope – Wide Field Camera 3". *NASA*. Archived from the original on November 13, 2021. Retrieved November 27, 2021.

[^56]: Hall, Donald N. B., ed. (1982). *The Space Telescope Observatory* (Technical report). NASA. CP-2244. Archived from the original on April 7, 2022. Retrieved April 7, 2022.

[^57]: "Hubble's Instruments: WFPC2 Wide Field Planetary Camera 2". *esahubble.org*. European Space Agency. Archived from the original on April 7, 2022. Retrieved April 7, 2022.

[^58]: Brandt, J. C.; Heap, S. R.; Beaver, E. A.; Boggess, A.; Carpenter, K. G.; Ebbets, D. C.; Hutchings, J. B.; Jura, M.; Leckrone, D. S. (1994). "The Goddard High Resolution Spectrograph: Instrument, goals, and science results". *Publications of the Astronomical Society of the Pacific*. **106**: 890–908. Bibcode:1994PASP..106..890B. doi:10.1086/133457. S2CID 120181145.

[^59]: Bless, R. C.; Walter, L. E.; White R. L. (1992) *High Speed Photometer Instrument Handbook* v 3.0 STSci.

[^60]: Benedict, G. Fritz; McArthur, Barbara E. (2005). Kurtz, D. W. (ed.). *High-precision stellar parallaxes from Hubble Space Telescope fine guidance sensors* (PDF). IAU Colloquium #196. *Transits of Venus: New Views of the Solar System and Galaxy*. Cambridge University Press. pp. 333–346. Bibcode:2005tvnv.conf..333B. doi:10.1017/S1743921305001511. S2CID 123078909. Archived from the original (PDF) on February 27, 2020.

[^61]: Edmondson, Frank K. (1997). *AURA and Its US National Observatories*. Cambridge University Press. p. 244. ISBN 978-0-521-55345-2. Archived from the original on July 15, 2022. Retrieved January 7, 2022.

[^62]: "About AURA". AURA. Archived from the original on September 29, 2018. Retrieved November 6, 2012.

[^63]: Dunar & Waring 1999, pp. 486–487.

[^64]: Roman, Nancy Grace. "Exploring the Universe: Space-Based Astronomy and Astrophysics", in *NASA SP-2001-4407: Exploring the Unknown* Archived January 20, 2017, at the Wayback Machine (PDF). NASA. Chapter 3, p. 536.

[^65]: "Closure of ST-ECF". *www.stecf.org*. Retrieved April 7, 2022.

[^66]: "Scheduling". *stsci.edu*. Space Telescope Science Institute. Archived from the original on July 15, 2022. Retrieved April 7, 2022.

[^67]: "Hubble's Deepest View of the Universe Unveils Bewildering Galaxies across Billions of Years". *HubbleSite.org*. Space Telescope Science Institute. January 15, 1996. Archived from the original on July 15, 2022. Retrieved April 7, 2022.

[^68]: Adler, David S.; Kinzel, Wayne; Jordan, Ian (August 6, 2014). Peck, Alison B.; Benn, Chris R.; Seaman, Robert L. (eds.). "Planning and scheduling at STScI: from Hubble to the James Webb Space Telescope". *Proc. SPIE 9149, Observatory Operations: Strategies, Processes, and Systems V*. Observatory Operations: Strategies, Processes, and Systems V. **9149**. Montréal, Quebec, Canada: 91490D. Bibcode:2014SPIE.9149E..0DA. doi:10.1117/12.2054932. S2CID 122694163. Archived from the original on July 15, 2022. Retrieved July 15, 2022.

[^69]: "HST Cycle 26 Primer Orbital Constraints – HST User Documentation". *hst-docs.stsci.edu*. Archived from the original on July 16, 2022. Retrieved July 16, 2022.

[^70]: Strolger & Rose 2017, p. 46.

[^71]: Tatarewicz 1998, p. 371.

[^72]: Wilford, John (April 9, 1990). "Telescope Is Set to Peer at Space and Time". *The New York Times*. Archived from the original on November 11, 2012. Retrieved January 19, 2009.

[^73]: "STS-31". NASA. Archived from the original on August 15, 2011. Retrieved April 26, 2008.

[^74]: "James Webb Space Telescope (JWST) Independent Comprehensive Review Panel (ICRP) Final Report" (PDF). NASA. p. 32. Archived (PDF) from the original on November 17, 2021. Retrieved April 7, 2022.

[^75]: *Powering Science: NASA's Large Strategic Science Missions*. The National Academies of Sciences, Engineering, and Medicine. 2017. p. 11, footnote 4. Bibcode:2017nap..book24857N. doi:10.17226/24857. ISBN 978-0-309-46383-6. Archived from the original on April 21, 2022. Retrieved April 7, 2022.

[^76]: Greenfieldboyce, Nell (November 18, 2009). "Camera That Saved Hubble Now On Display". *NPR*. Archived from the original on December 30, 2021. Retrieved April 7, 2022.

[^77]: Harwood, William (April 22, 2015). "How NASA fixed Hubble's flawed vision – and reputation". *CBS News*. Archived from the original on April 7, 2022. Retrieved April 7, 2022.

[^78]: "Greater accuracy deepens understanding – Hubble's Faint Object Spectrograph re-calibrated". *ESA/Hubble*. September 11, 2001. Archived from the original on July 15, 2022. Retrieved April 7, 2022.

[^79]: "Hubble's Instruments: FOC – Faint Object Camera". *ESA/Hubble*. Archived from the original on May 4, 2022. Retrieved April 7, 2022.

[^80]: Devitt, Terry (April 21, 2015). "Wisconsin contributions helped Hubble Space Telescope soar". *University of Wisconsin-Madison News*. Archived from the original on December 24, 2021. Retrieved April 7, 2022.

[^81]: Plait, Phil (1999). "Hubble's Next Next Generation". *Bitesize astronomy*. Archived from the original on May 31, 2022. Retrieved April 7, 2022.

[^82]: "Hubble Space Telescope Wide Field Camera 3: Capabilities and Scientific Programs" (PDF). *Space Telescope Science Institute*. 2001. Archived (PDF) from the original on July 15, 2022. Retrieved April 6, 2022.

[^83]: Burrows, Christopher J.; Holtzman, Jon A.; Faber, S. M.; Bely, Pierre Y.; et al. (March 10, 1991). "The imaging performance of the Hubble Space Telescope". *Astrophysical Journal Letters*. **369**: L21–L25. Bibcode:1991ApJ...369L..21B. doi:10.1086/185950.

[^84]: McMaster, Matt; Biretta, John (2008). "WFPC2 Instrument Handbook" (PDF). 10.0. Baltimore: STScI. Chapter 5.1. Archived (PDF) from the original on July 15, 2022. Retrieved April 7, 2022.

[^85]: "Servicing Mission 1". NASA. Archived from the original on April 20, 2008. Retrieved March 28, 2016.

[^86]: Tatarewicz 1998, p. 375.

[^87]: Powell, Corey S. (April 24, 2015). "The Many Resurrections of the Hubble Space Telescope". *Discover Magazine*. Archived from the original on July 15, 2022. Retrieved December 16, 2020.

[^88]: Tatarewicz 1998, p. 373.

[^89]: Goodwin, Irwin; Cioffi, Denis F. (1994). "Hubble repair improves vision and helps restore NASA's image". *Physics Today*. **47** (3): 42. Bibcode:1994PhT....47c..42G. doi:10.1063/1.2808434.

[^90]: Dunar & Waring 1999, pp. 514–515.

[^91]: Allen et al. 1990, p. 7-1: The spacing of the field lens in the corrector was to have been done by laser measurements off the end of an invar bar. Instead of illuminating the end of the bar, however, the laser in fact was reflected from a worn spot on a black-anodized metal cap placed over the end of the bar to isolate its center (visible through a hole in the cap). The technician who performed the test noted an unexpected gap between the field lens and its supporting structure in the corrector and filled it in with an ordinary metal washer.

[^92]: Dunar & Waring 1999, p. 512: "the firm's optical operations personnel dismissed the evidence as itself flawed. They believed the other two null correctors were less accurate than the reflective null corrector and so could not verify its reliability. Since they assumed the perfection of the mirror and reflective null corrector, they rejected falsifying information from independent tests, believed no problems existed, and reported only good news."

[^93]: Allen et al. 1990, p. 10-1.

[^94]: Tatarewicz 1998, p. 374.

[^95]: Pellerin, Charles J. (2009). *How NASA Builds Teams: Mission Critical Soft Skills for Scientists, Engineers, and Project Teams*. Wiley. p. 8. ISBN 9780470456484.

[^96]: "NASA Plans Mission by 1994 to Repair Hubble Telescope". *The New York Times*. July 3, 1991.

[^97]: Chaisson, Eric (1994). *The Hubble wars: astrophysics meets astropolitics in the two-billion-dollar struggle over the Hubble Space Telescope*. Internet Archive. New York: HarperCollins Publishers. p. 184. ISBN 978-0-06-017114-8.

[^98]: Fisher, Arthur (October 1990). "The Trouble with Hubble". *Popular Science*: 100. Archived from the original on January 8, 2022. Retrieved November 8, 2012.

[^99]: Litvac, M. M. (1991). *Image inversion analysis of the HST OTA (Hubble Space Telescope Optical Telescope Assembly), phase A* (Technical report). TRW, Inc. Space and Technology Group. Bibcode:1991trw..rept.....L.

[^100]: Redding, David C.; Sirlin, S.; Boden, A.; Mo, J.; Hanisch, B.; Furey, L. (July 1995). "Optical Prescription of the HST" (PDF). *Calibrating Hubble Space Telescope. Post Servicing Mission*. NASA JPL: 132. Bibcode:1995chst.conf..132R. hdl:2014/31621. Archived from the original (PDF) on May 1, 2015.

[^101]: Allen et al. 1990, pp. E-1.

[^102]: Tatarewicz 1998, p. 376.

[^103]: Jedrzejewski, R. I.; Hartig, G.; Jakobsen, P.; Ford, H. C. (1994). "In-orbit performance of the COSTAR-corrected Faint Object Camera". *Astrophysical Journal Letters*. **435**: L7–L10. Bibcode:1994ApJ...435L...7J. doi:10.1086/187581.

[^104]: "HST". STScI. Corrective Optics Space Telescope Axial Replacement. Archived from the original on July 15, 2022. Retrieved November 4, 2012.

[^105]: "Camera That Saved Hubble Now On Display". *NPR*. Archived from the original on December 30, 2021. Retrieved December 30, 2021.

[^106]: "Hubble Essentials". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on October 28, 2012. Retrieved November 8, 2012.

[^107]: "Hubble Space Telescope (HST) Archive System". February 19, 2013. Archived from the original on February 19, 2013. Retrieved January 31, 2024.

[^108]: Treat, Jason; Scalamogna, Anna; Conant, Eve (2015). "The Secret to Hubble's Success". *National Geographic*. Archived from the original on April 28, 2015. Retrieved April 25, 2015.

[^109]: Overbye, Jason; Corum, Jonathan; Drakeford, Jason (April 24, 2015). "Hubble Reflects the Cosmos". *The New York Times*. Archived from the original on February 2, 2019. Retrieved April 25, 2015.

[^110]: Tatarewicz 1998, pp. 374, 378, 381, 388.

[^111]: Tatarewicz 1998, pp. 380–381, 384–387.

[^112]: Tatarewicz 1998, pp. 384–387.

[^113]: Trauger, J. T.; Ballester, G. E.; Burrows, C. J.; Casertano, S.; et al. (1994). "The on-orbit performance of WFPC2". *Astrophysical Journal Letters*. **435**: L3–L6. Bibcode:1994ApJ...435L...3T. doi:10.1086/187580. Archived from the original on January 7, 2022. Retrieved January 7, 2022.

[^114]: DeVorkin, David (April 24, 2020). "Telling Hubble's Story for 30 Years". *National Air and Space Museum*. Smithsonian Institution. Archived from the original on December 31, 2021. Retrieved April 7, 2022.

[^115]: "Servicing Mission 2". NASA. Archived from the original on April 19, 2008. Retrieved April 26, 2008.

[^116]: "NICMOS Thermal History". STScI. Retrieved April 26, 2008.

[^117]: "Servicing Mission 3A Overview". NASA. Archived from the original on May 9, 2008. Retrieved April 26, 2008.

[^118]: "Servicing Mission 3". NASA. Archived from the original on April 7, 2008. Retrieved April 26, 2008.

[^119]: "Servicing Mission 4 Cancelled". STScI. January 16, 2004. Archived from the original on May 11, 2008. Retrieved April 28, 2008.

[^120]: *Assessment of Options for Extending the Life of the Hubble Space Telescope: Final Report*. The National Academies. 2005. doi:10.17226/11169. ISBN 978-0-309-09530-3. Archived from the original on July 15, 2022. Retrieved December 9, 2012. Chapter 7, "Given the intrinsic value of a serviced Hubble, and the high likelihood of success for a shuttle servicing mission, the committee judges that such a mission is worth the risk."

[^121]: "Ariane 5 goes down in history with successful launch of Webb". *Arianespace* (Press release). December 25, 2021. Archived from the original on March 10, 2022. Retrieved December 25, 2021.

[^122]: "2004 Annual Report" (PDF). Astronomy and Astrophysics Advisory Committee. March 15, 2004. Section 3.1 – The Scientific Impact of the HST SM4 Cancellation. Archived (PDF) from the original on March 27, 2019. Retrieved November 5, 2012.

[^123]: Guinnessy, Paul (September 2003). "Astronomers Lobby for New Lease on Hubble's Life". *Physics Today*. **56** (9): 29–31. Bibcode:2003PhT....56i..29G. doi:10.1063/1.1620825. Archived from the original on July 15, 2022. Retrieved April 6, 2022.

[^124]: Leary, Warren E. (July 14, 2004). "Panel Urges NASA to Save Hubble Space Telescope". *The New York Times*. Archived from the original on February 16, 2018. Retrieved November 8, 2012.

[^125]: Gugliotta, Guy (April 12, 2005). "Nominee Backs a Review of NASA's Hubble Decision". *The Washington Post*. Archived from the original on July 6, 2017. Retrieved January 10, 2007.

[^126]: "Mikulski Vows To Fight For Hubble" (Press release). Barbara Mikulski. February 7, 2005. Archived from the original on April 30, 2008. Retrieved April 26, 2008.

[^127]: Boyle, Alan (October 31, 2006). "NASA gives green light to Hubble rescue". NBC News. Archived from the original on November 4, 2013. Retrieved January 10, 2007.

[^128]: Cowen, Ron (September 29, 2008). "Hubble suddenly quiet". ScienceNews. Retrieved November 8, 2012.

[^129]: Courtland, Rachel (October 28, 2008). "Hubble re-opens an eye". *New Scientist*. Archived from the original on October 29, 2008. Retrieved October 29, 2008.

[^130]: "NASA Sets Target Shuttle Launch Date for Hubble Servicing Mission". NASA. December 4, 2008. Archived from the original on December 6, 2008. Retrieved December 5, 2008.

[^131]: "Hubble Opens New Eyes on the Universe". NASA. September 9, 2009. Archived from the original on May 27, 2012. Retrieved May 28, 2012.

[^132]: "The Soft Capture and Rendezvous System". NASA. Archived from the original on September 11, 2008. Retrieved May 20, 2009.

[^133]: Overbye, Dennis (September 9, 2009). "After Hubble Repair, New Images From Space". *The New York Times*. Archived from the original on November 21, 2015. Retrieved August 1, 2015.

[^134]: Overbye, Dennis (May 17, 2009). "After a Yank, 'Surgery' on Hubble Optics". *The New York Times*. Archived from the original on October 4, 2013. Retrieved August 1, 2015.

[^135]: "Repair of the Advanced Camera for Surveys". *SpaceTelescope.org*. Retrieved August 1, 2015.

[^136]: "Outer Planet Atmospheres Legacy (OPAL)". Archived from the original on March 30, 2023. Retrieved March 30, 2023.

[^137]: "Hubble explores the origins of modern galaxies". *SpaceTelescope.org*. August 15, 2013. heic1315. Archived from the original on November 24, 2020. Retrieved October 4, 2013.

[^138]: "Survey Description". *CANDELS*. Archived from the original on October 20, 2013. Retrieved October 4, 2013 – via UCOLick.org.

[^139]: "Hubble Deep Fields Initiative 2012 Science Working Group Report" (PDF). *STScI.edu*. 2012. Archived from the original on July 15, 2022. Retrieved June 29, 2015.

[^140]: "Hubble Space Telescope: Frontier Fields". *STScI.edu*. Archived from the original on July 15, 2022. Retrieved October 4, 2013.

[^141]: "Home Page". *COSMOS*. Archived from the original on January 5, 2016. Retrieved August 31, 2019.

[^142]: "For Astronomers". *COSMOS*. Archived from the original on October 25, 2020. Retrieved November 2, 2020.

[^143]: "Hubble Maps the Cosmic Web of "Clumpy" Dark Matter in 3-D". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on July 15, 2022. Retrieved November 2, 2020.

[^144]: "CLASH: Cluster Lensing And Supernova survey with Hubble". Space Telescope Science Institute. Retrieved March 27, 2025.

[^145]: "Hubble's panoramic view of the Andromeda Galaxy (annotated)". *www.esahubble.org*. Retrieved March 27, 2025. This article incorporates text from this source, which is in the public domain.

[^146]: "Hubble M31 PHAT Mosaic". Space Telescope Science Institute. Retrieved March 27, 2025.

[^147]: Chen Z, Williams B, Lang D, Dolphin A, Durbin M, Dalcanton JJ, Smercina A, Girardi L, Murray CE, Bell EF, Boyer ML, D'Souza R, Gilbert K, Gordon K, Guhathakurta P, Hammer F, Johnson LC, Lauer TR, Lazzarini M, Murphy JW, Patel E, Quirk A, Díaz Rodríguez M, Roman-Duval JC, Sanderson RE, Seth A, Wainer TM, Weisz DR (2025). "PHAST. The Panchromatic Hubble Andromeda Southern Treasury. I. Ultraviolet and Optical Photometry of over 90 Million Stars in M31". *The Astrophysical Journal*. **979** (1): 35. Bibcode:2025ApJ...979...35C. doi:10.3847/1538-4357/ad7e2b.

[^148]: "NASA's Hubble Traces Hidden History of Andromeda Galaxy". Space Telescope Science Institute. January 16, 2025. Retrieved March 27, 2025.

[^149]: Dalcanton, JJ, Williams, BF, Lang, D, Lauer, TR, Kalirai, JS, Seth, AC, Dolphin, A, Rosenfield, P, Weisz, DR, Bell, EF, Bianchi, LC, Boyer, ML, Caldwell, N, Dong, H, Dorman, CE, Gilbert, KM, Girardi, L, Gogarten, SM, Gordon, KD, Guhathakurta, P, Hodge, PW, Holtzman, JA, Johnson, LC, Larsen, SS, Lewis, A, Melbourne, JL, Olsen, KAG, Rix, HW, Rosema, K, Saha, A, Sarajedini, A, Skillman, ED, Stanek, KZ (2012). "The Panchromatic Hubble Andromeda Treasury". *The Astrophysical Journal Supplement*. **200** (2): 18. arXiv:1204.0010. Bibcode:2012ApJS..200...18D. doi:10.1088/0067-0049/200/2/18.

[^150]: Strolger & Rose 2017, p. 11.

[^151]: "HST Overview". NASA. June 21, 2010. Mission Operations and Observations. Archived from the original on July 15, 2022. Retrieved November 4, 2012.

[^152]: "Team Hubble". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on October 28, 2012. Retrieved November 5, 2012.

[^153]: Strolger & Rose 2017, p. 21.

[^154]: Strolger & Rose 2017, p. 37.

[^155]: O'Meara, Stephen James (June 1997). Aguirre, Edwin L. (ed.). "The Demise of the HST Amateur Program". *Sky & Telescope*. **96** (6): 97. Bibcode:1997S&T....93f..97O. Archived from the original on February 9, 2019. Retrieved February 9, 2019.

[^156]: Walthert, Matthew (April 24, 2015). "Open Mic Night at the Hubble Telescope". *Motherboard*. Archived from the original on April 7, 2022. Retrieved April 6, 2022.

[^157]: "Hubble's Hidden Treasures 2012". *ESA/Hubble*. Archived from the original on May 2, 2022. Retrieved April 7, 2022.

[^158]: Goddard, Louis (August 27, 2012). "Hubble image processing competition creates stunning new views from old data". *The Verge*. Archived from the original on April 7, 2022. Retrieved April 7, 2022.

[^159]: Secosky, James J.; Potter, Michael (September 1994). "A Hubble Space Telescope Study of Posteclipse Brightening and Albedo Changes on Io". *Icarus*. **111** (1): 73–78. Bibcode:1994Icar..111...73S. doi:10.1006/icar.1994.1134.

[^160]: Storrs, Alex; Weiss, Ben; Zellner, Ben; Burleson, Win; et al. (February 1999). "Imaging Observations of Asteroids with Hubble Space Telescope" (PDF). *Icarus*. **137** (2): 260–268. Bibcode:1999Icar..137..260S. doi:10.1006/icar.1999.6047. Archived from the original (PDF) on February 25, 2012.

[^161]: "NASA's Hubble Space Telescope Views Major Storm On Saturn". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on July 15, 2022. Retrieved October 22, 2020.

[^162]: Wilber, S.; Tatum, R.; Kidger, M.; Gonzalez, V.; Hernandez, F. (October 1, 1990). "Saturn". *International Astronomical Union Circular* (5109): 1. Bibcode:1990IAUC.5109....1W. Archived from the original on July 15, 2022. Retrieved October 22, 2020.

[^163]: "HST Proposal Search". *archive.stsci.edu*. Archived from the original on July 15, 2022. Retrieved October 22, 2020.

[^164]: "HST Proposal Search". *archive.stsci.edu*. Archived from the original on July 15, 2022. Retrieved October 22, 2020.

[^165]: Keel, William C.; Maksym, W. Peter; Bennert, Vardha N.; Lintott, Chris J.; Chojnowski, S. Drew; Moiseev, Alexei; Smirnova, Aleksandrina; Schawinski, Kevin; Urry, C. Megan; Evans, Daniel A.; Pancoast, Anna (May 1, 2015). "HST Imaging of Fading AGN Candidates. I. Host-galaxy Properties and Origin of the Extended Gas". *The Astronomical Journal*. **149** (5): 155. arXiv:1408.5159. Bibcode:2015AJ....149..155K. doi:10.1088/0004-6256/149/5/155.

[^166]: Henry, Alaina; Scarlata, Claudia; Martin, Crystal L.; Erb, Dawn (August 1, 2015). "Lyalpha Emission from Green Peas: The Role of Circumgalactic Gas Density, Covering, and Kinematics". *The Astrophysical Journal*. **809** (1): 19. arXiv:1505.05149. Bibcode:2015ApJ...809...19H. doi:10.1088/0004-637X/809/1/19. S2CID 119210958. Archived from the original on July 15, 2022. Retrieved October 22, 2020.

[^167]: "HST Proposal Search". *archive.stsci.edu*. Archived from the original on July 15, 2022. Retrieved October 22, 2020.

[^168]: "Hubble Images Suggest Rogue Asteroid Smacked Jupiter". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on July 15, 2022. Retrieved October 22, 2020.

[^169]: "Hubble Confirms New Dark Spot on Neptune". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on July 15, 2022. Retrieved October 22, 2020.

[^170]: Bardalez Gagliuffi, Daniella C.; Faherty, Jacqueline K.; Schneider, Adam C.; Meisner, Aaron; Caselden, Dan; Colin, Guillaume; Goodman, Sam; Kirkpatrick, J. Davy; Kuchner, Marc; Gagné, Jonathan; Logsdon, Sarah E. (June 1, 2020). "WISEA J083011.95+283716.0: A Missing Link Planetary-mass Object". *The Astrophysical Journal*. **895** (2): 145. arXiv:2004.12829. Bibcode:2020ApJ...895..145B. doi:10.3847/1538-4357/ab8d25. S2CID 216553879.

[^171]: Bahcall, J. N.; Bergeron, J.; Boksenberg, A.; Hartig, G. F.; Jannuzi, B. T.; Kirhakos, S.; Sargent, W. L. W.; Savage, B. D.; et al. (1993). "The Hubble Space Telescope Quasar Absorption Line Key Project. I. First Observational Results, Including Lyman-Alpha and Lyman-Limit Systems". *The Astrophysical Journal Supplement Series*. **87**: 1–43. Bibcode:1993ApJS...87....1B. doi:10.1086/191797.

[^172]: Ostrander, E. J.; Nichol, R. C.; Ratnatunga, K. U.; Griffiths, R. E. (1998). "The Hubble Space Telescope Medium Deep Survey Cluster Sample: Methodology and Data". *The Astronomical Journal*. **116** (6): 2644–2658. arXiv:astro-ph/9808304. Bibcode:1998AJ....116.2644O. doi:10.1086/300627. S2CID 11338445.

[^173]: Huchra, John (2008). "The Hubble Constant". Retrieved January 11, 2011.

[^174]: Freedman, W. L.; Madore, B. F.; Gibson, B.K.; Ferrarese, L.; Kelson, D. D.; Sakai, S.; Mould, J. R.; Kennicutt, R. C. Jr.; et al. (2001). "Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant". *The Astrophysical Journal*. **553** (1): 47–72. arXiv:astro-ph/0012376. Bibcode:2001ApJ...553...47F. doi:10.1086/320638. S2CID 119097691.

[^175]: Palmer, Roxanne (April 24, 2015). "25 of the Greatest Hubble Telescope Discoveries From the Past 25 Years". World Science Festival. Archived from the original on March 6, 2016. Retrieved February 23, 2016.

[^176]: Weinberg, Steven (2008). *Cosmology*. Oxford University Press. ISBN 978-0-19-852682-7.

[^177]: Clifton, Timothy; Ferreira, Pedro G. (March 23, 2009). "Does Dark Energy Really Exist?". *Scientific American*. **300** (4): 48–55. Bibcode:2009SciAm.300d..48C. doi:10.1038/scientificamerican0409-48. PMID 19363920. Archived from the original on September 28, 2011. Retrieved June 16, 2009.

[^178]: Seife, Charles (June 20, 2003). "Dark Energy Tiptoes Toward the Spotlight". *Science*. **300** (5627): 1896–1897. doi:10.1126/science.300.5627.1896. PMID 12817137. S2CID 42463717.

[^179]: "Hubble Confirms Existence of Massive Black Hole at Heart of Active Galaxy". Goddard Space Flight Center. May 25, 1994. Archived from the original on September 18, 2011. Retrieved April 26, 2008.

[^180]: Gebhardt, K.; Bender, R.; Bower, G.; Dressler, A.; et al. (2000). "A Relationship between Nuclear Black Hole Mass and Galaxy Velocity Dispersion". *The Astrophysical Journal*. **539** (1): L13–L16. arXiv:astro-ph/0006289. Bibcode:2000ApJ...539L..13G. doi:10.1086/312840. S2CID 11737403.

[^181]: Ferrarese, Laura; Merritt, David (2000). "A Fundamental Relationship between Supermassive Black Holes and their Host Galaxies". *The Astrophysical Journal*. **539** (1): L9–L12. arXiv:astro-ph/0006053. Bibcode:2000ApJ...539L...9F. doi:10.1086/312838. S2CID 6508110.

[^182]: "Hubble spots three magnified views of most distant known galaxy". *ESA/Hubble*. November 15, 2012. Archived from the original on March 1, 2013. Retrieved April 6, 2022.

[^183]: Brumfiel, Geoff (September 19, 2008). "How they wonder what you are". *Nature News*. doi:10.1038/news.2008.1122. Archived from the original on January 3, 2019. Retrieved November 4, 2012.

[^184]: Gänsicke, B. T.; Levan, A. J.; Marsh, T. R.; Wheatley, P. J. (2009). "SCP06F6: A carbon-rich extragalactic transient at redshift z~0.14?". *The Astrophysical Journal*. **697** (1): L129–L132. arXiv:0809.2562. Bibcode:2009ApJ...697L.129G. doi:10.1088/0004-637X/697/2/L129. S2CID 14807033.

[^185]: Oesch, P. A.; Brammer, G.; van Dokkum, P.; et al. (March 2016). "A Remarkably Luminous Galaxy at *z* =11.1 Measured with *Hubble Space Telescope* Grism Spectroscopy". *The Astrophysical Journal*. **819** (2). 129. arXiv:1603.00461. Bibcode:2016ApJ...819..129O. doi:10.3847/0004-637X/819/2/129. S2CID 119262750.

[^186]: "Hubble Team Breaks Cosmic Distance Record". *HubbleSite.org*. Space Telescope Science Institute. March 3, 2016. STScI-2016-07. Archived from the original on May 21, 2022. Retrieved April 7, 2022.

[^187]: Klotz, Irene (March 3, 2016). "Hubble Spies Most Distant, Oldest Galaxy Ever". *Discovery News*. Archived from the original on May 11, 2016. Retrieved March 3, 2016.

[^188]: "In Depth | P/Shoemaker-Levy 9". *NASA Solar System Exploration*. July 27, 2021. Archived from the original on February 2, 2022. Retrieved April 7, 2022.

[^189]: "NASA's Hubble Observations Suggest Underground Ocean on Jupiter's Largest Moon". *HubbleSite.org*. Space Telescope Science Institute. March 12, 2015. Archived from the original on July 15, 2022. Retrieved April 7, 2022.

[^190]: Saur, Joachim; Duling, Stefan; Roth, Lorenz; Jia, Xianzhe; et al. (March 2015). "The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals". *Journal of Geophysical Research*. **120** (3): 1715–1737. Bibcode:2015JGRA..120.1715S. doi:10.1002/2014JA020778. hdl:2027.42/111157. Archived from the original on July 20, 2018. Retrieved August 25, 2019.

[^191]: Nemiroff, R.; Bonnell, J., eds. (March 11, 1996). "Hubble Telescope Maps Pluto". *Astronomy Picture of the Day*. NASA. Retrieved April 26, 2008.

[^192]: "Astronomers Measure Mass of Largest Dwarf Planet". *HubbleSite.org*. Space Telescope Science Institute. June 14, 2007. Archived from the original on December 14, 2023. Retrieved April 7, 2022.

[^193]: Brown, Mike (2010). *How I Killed Pluto and Why It Had It Coming* (1st ed.). New York: Spiegel & Grau. pp. 108, 191. ISBN 978-0-385-53108-5. OCLC 495271396.

[^194]: Showalter, M. R.; Weaver, H. A.; Stern, S. A.; Steffl, A. J.; Buie, M. W.; Merline, W. J.; Mutchler, M. J.; Soummer, R.; Throop, H. B. (2012). "New Satellite of (134340) Pluto: S/2012 (134340) 1". *International Astronomical Union Circular* (9253): 1. Bibcode:2012IAUC.9253....1S.

[^195]: "Hubble recruited to find New Horizons probe post-Pluto target". *nasaspaceflight.com*. June 16, 2014. Archived from the original on June 21, 2019. Retrieved February 1, 2020.

[^196]: Brown, Dwayne; Villard, Ray (October 15, 2014). "RELEASE 14-281 NASA's Hubble Telescope Finds Potential Kuiper Belt Targets for New Horizons Pluto Mission". *NASA*. Archived from the original on April 6, 2020. Retrieved October 16, 2014.

[^197]: Buie, Marc (October 15, 2014). "New Horizons HST KBO Search Results: Status Report" (PDF). Space Telescope Science Institute. p. 23. Archived from the original (PDF) on July 27, 2015. Retrieved February 1, 2020.

[^198]: Corum, Jomathan (February 10, 2019). "New Horizons Glimpses the Flattened Shape of Ultima Thule". *The New York Times*. Archived from the original on December 24, 2021. Retrieved February 1, 2020.

[^199]: Jewitt, David (April 12, 2022). "Hubble Confirms Largest Comet Nucleus Ever Seen". *NASA.GOV*. Archived from the original on April 14, 2022. Retrieved April 13, 2022.

[^200]: "ALMA and VLT Find Evidence for Stars Forming Just 250 Million Years After Big Bang". *eso.org*. Archived from the original on May 16, 2018. Retrieved May 18, 2018.

[^201]: Diego, J. M.; Broadhurst, T.; Chen, C.; Lim, J.; Zitrin, A.; Chan, B.; Coe, D.; Ford, H. C.; Lam, D.; Zheng, W. (2016). "A Free-Form Prediction for the Reappearance of Supernova Refsdal in the Hubble Frontier Fields Cluster MACSJ1149.5+2223". *Monthly Notices of the Royal Astronomical Society*. **456** (1): 356–365. arXiv:1504.05953. Bibcode:2016MNRAS.456..356D. doi:10.1093/mnras/stv2638.

[^202]: Kelly, P. L.; Rodney, S. A.; Treu, T.; Strolger, L.-G.; Foley, R. J.; Jha, S. W.; Selsing, J.; Brammer, G.; Bradač, M.; Cenko, S. B.; Graur, O. (February 23, 2016). "Deja Vu All Over Again: The Reappearance of Supernova Refsdal". *The Astrophysical Journal*. **819** (1): L8. arXiv:1512.04654. Bibcode:2016ApJ...819L...8K. doi:10.3847/2041-8205/819/1/L8. hdl:1885/153586. S2CID 32126257.

[^203]: Watkins, Laura L.; van der Marel, Roeland P.; Sohn, Sangmo Tony; Wyn Evans, N. (March 12, 2019). "Evidence for an Intermediate-mass Milky Way from Gaia DR2 Halo Globular Cluster Motions". *The Astrophysical Journal*. **873** (2): 118. arXiv:1804.11348. Bibcode:2019ApJ...873..118W. doi:10.3847/1538-4357/ab089f. S2CID 85463973.

[^204]: "Hubble Confirms Abundance of Protoplanetary Disks around Newborn Stars". *HubbleSite.org*. Space Telescope Science Institute. June 13, 1994. Archived from the original on April 7, 2022. Retrieved April 7, 2022.

[^205]: "Hubble Finds Extrasolar Planets Far Across Galaxy". NASA. October 4, 2006. Archived from the original on August 23, 2011. Retrieved April 26, 2008.

[^206]: "Autopsy of an Explosion". NASA. March 26, 1999. Archived from the original on April 15, 2008. Retrieved April 26, 2008.

[^207]: Toft, Sune; Zabl, Johannes; Richard, Johan; Gallazzi, Anna; Zibetti, Stefano; Prescott, Moire; Grillo, Claudio; Man, Allison W. S.; Lee, Nicholas Y.; Gómez-Guijarro, Carlos; Stockmann, Mikkel; Magdis, Georgios; Steinhardt, Charles L. (2017). "A massive, dead disk galaxy in the early Universe". *Nature*. **546** (7659): 510–513. arXiv:1706.07030. Bibcode:2017Natur.546..510T. doi:10.1038/nature22388. PMC 6485677. PMID 28640271.

[^208]: "Record Broken: Hubble Spots Farthest Star Ever Seen". March 29, 2022. Archived from the original on March 30, 2022. Retrieved March 31, 2022.

[^209]: "HST Publication Statistics". STScI. Archived from the original on May 14, 2019. Retrieved December 26, 2017.

[^210]: Meylan, Georges; Madrid, Juan; Macchetto, Duccio (Spring 2003). "Hubble Science Metrics" (PDF). *Newsletter*. **20** (2). Space Telescope Science Institute. Archived (PDF) from the original on October 9, 2022.

[^211]: Benn, C. R.; Sánchez, S. F. (2001). "Scientific Impact of Large Telescopes". *Publications of the Astronomical Society of the Pacific*. **113** (781): 385–396. arXiv:astro-ph/0010304. Bibcode:2001PASP..113..385B. doi:10.1086/319325. S2CID 204931773.

[^212]: Haniff, C. A.; Mackay, C. D.; Titterington, D. J.; Sivia, D.; et al. (August 1987). "The first images from optical aperture synthesis". *Nature*. **328** (6132): 694–696. Bibcode:1987Natur.328..694H. doi:10.1038/328694a0. S2CID 4281897.

[^213]: Buscher, D. F.; Baldwin, J. E.; Warner, P. J.; Haniff, C. A. (July 1990). "Detection of a bright feature on the surface of Betelgeuse". *Monthly Notices of the Royal Astronomical Society*. **245**: 7. Bibcode:1990MNRAS.245P...7B.

[^214]: Williams, Robert (April 1, 2020). "Hubble telescope 30 years in orbit: personal reflections". *Research in Astronomy and Astrophysics*. **20** (4): 044. arXiv:2004.12132. Bibcode:2020RAA....20...44W. doi:10.1088/1674-4527/20/4/44. S2CID 218517143. Archived from the original on April 7, 2022. Retrieved April 7, 2022.

[^215]: Max, Claire (2001). "Introduction to Adaptive Optics and its History" (PDF). *Center for Adaptive Optics*. Archived (PDF) from the original on April 12, 2022. Retrieved April 7, 2022.

[^216]: Lallo, Matthew D. (January 2012). "Experience with the Hubble Space Telescope: 20 years of an archetype". *Optical Engineering*. **51** (1). 011011. arXiv:1203.0002. Bibcode:2012OptEn..51a1011L. doi:10.1117/1.OE.51.1.011011. S2CID 15722152.

[^217]: "Gyroscopes". ESA. Archived from the original on May 7, 2012. Retrieved June 9, 2012.

[^218]: "Servicing Mission 4 Essentials". NASA. September 15, 2008. Archived from the original on May 3, 2019. Retrieved December 14, 2020.

[^219]: "Hubble stretches the stellar tape measure ten times further". *ESA/Hubble Images*. Archived from the original on October 30, 2017. Retrieved April 12, 2014.

[^220]: Rosen, Raphael (July 24, 2013). "The Secret Science of the Hubble Space Telescope's Amazing Images". *Space.com*. Archived from the original on May 12, 2019. Retrieved July 26, 2013.

[^221]: Hester, Jeff (July 1, 2008). "How Hubble Sees". *Nova ScienceNow*. PBS. Archived from the original on October 15, 2018. Retrieved August 17, 2015.

[^222]: "The Hubble Telescope". STScI. Retrieved April 26, 2008.

[^223]: "CADC's Hubble Space Telescope Archive". CADC. Archived from the original on April 19, 2022. Retrieved April 11, 2022.

[^224]: "European HST Archive at ESA/ESAC". ESA/ESAC. Archived from the original on May 25, 2013. Retrieved February 14, 2013.

[^225]: Strolger & Rose 2017, p. 53.

[^226]: Rose 2017, p. 69.

[^227]: "The Hubble Heritage Project". STScI. Archived from the original on September 22, 2018. Retrieved November 5, 2012.

[^228]: Rose 2017, pp. 67–69.

[^229]: Rose 2017, pp. 68–69.

[^230]: "National Aeronautics and Space Administration 2003 Strategic Plan" (PDF). NASA. Archived from the original (PDF) on November 16, 2012. Retrieved November 5, 2012.

[^231]: Kessler, Elizabeth A. (April 24, 2020). "How Hubble Changed the Way We Picture Our Universe". *National Air and Space Museum*. Smithsonian Institution. Archived from the original on April 7, 2022. Retrieved April 7, 2022.

[^232]: "The European Homepage for the NASA/ESA Hubble Space Telescope". European Space Agency. Archived from the original on February 21, 2011. Retrieved April 26, 2008.

[^233]: "Hubblecast". European Space Agency. Archived from the original on April 18, 2019. Retrieved April 26, 2015.

[^234]: "Historic Hubble Space Telescope Repair Mission Team Honored by the Space Foundation with 2010 Space Achievement Award" (Press release). 26th National Space Symposium. March 29, 2010. Archived from the original on March 6, 2012. Retrieved November 5, 2012.

[^235]: "Things to Do | Hubble Space Telescope Replica". *Visit Missouri*. Missouri Division of Tourism. Archived from the original on May 31, 2022. Retrieved April 6, 2022.

[^236]: "Starry-Eyed Hubble Celebrates 20 Years of Awe and Discovery". *HubbleSite.org*. Space Telescope Science Institute. April 22, 2010. Archived from the original on July 15, 2022. Retrieved April 7, 2022.

[^237]: "25th Anniversary Image: Westerlund 2". Space Telescope Science Institute. Archived from the original on January 24, 2019. Retrieved April 24, 2015.

[^238]: "Celebrating 25 years of the NASA/ESA Hubble Space Telescope". European Space Agency. Archived from the original on December 14, 2023. Retrieved April 24, 2015.

[^239]: "Hubble captures birthday bubble". *SpaceTelescope.org*. European Space Agency. April 21, 2016. Archived from the original on February 6, 2019. Retrieved December 15, 2016.

[^240]: Sembach, K. R.; et al. (October 2004). "Handbook Archive – HST Two-Gyro Handbook". 1.0. Baltimore, Maryland: Space Telescope Science Institute. Archived from the original on July 15, 2022. Retrieved April 11, 2022.

[^241]: Beasley, Dolores; Hendrix, Susan; Weaver, Donna (August 31, 2005). "Hubble Space Telescope Begins 'Two-Gyro' Science Operations". NASA. Archived from the original on May 8, 2017. Retrieved February 8, 2019.

[^242]: Hecht, Jeff (September 6, 2007). "Hubble telescope loses another gyroscope". *New Scientist*. Archived from the original on January 22, 2012. Retrieved January 6, 2009.

[^243]: Harwood, William (October 30, 2008). "Endeavour to go Nov. 14; Hubble slips deeper into '09". *Spaceflight Now*. Archived from the original on December 19, 2008. Retrieved January 6, 2009.

[^244]: Garner, Rob (October 8, 2018). "Update on the Hubble Space Telescope Safe Mode". NASA. Archived from the original on October 12, 2018. Retrieved October 15, 2018.

[^245]: Rincon, Paul (October 8, 2018). "Hubble telescope hit by mechanical failure". *BBC News*. Archived from the original on October 10, 2018. Retrieved October 10, 2018.

[^246]: Foust, Jeff (October 22, 2018). "NASA makes progress on fixing Hubble gyro". Space News. Retrieved October 23, 2018.

[^247]: Molina, Brett (October 24, 2018). "What fixed NASA's Hubble Space Telescope? Someone flipped a switch on and off". *USA Today*. Archived from the original on April 11, 2019. Retrieved February 8, 2019.

[^248]: Wang, Amy B. (October 24, 2018). "No, NASA didn't fix the Hubble Telescope by just turning it off and on again". *The Washington Post*. Archived from the original on December 31, 2018. Retrieved February 8, 2019.

[^249]: Chou, Felicia (October 27, 2018). "NASA's Hubble Space Telescope Returns to Science Operations". NASA. Archived from the original on February 8, 2019. Retrieved February 8, 2019.

[^250]: "Space Telescope Imaging Spectrograph". STScI. Retrieved April 26, 2008.

[^251]: Garner, Rob (June 2, 2012). "Hubble Servicing Missions | Servicing Mission 4". *NASA*. Archived from the original on April 6, 2022. Retrieved April 6, 2022.

[^252]: "Engineers Investigate Issue on One of Hubble's Science Instruments". NASA. January 29, 2007. Archived from the original on May 14, 2007. Retrieved April 26, 2008.

[^253]: "Advanced Camera for Surveys". STScI. Retrieved May 21, 2009.

[^254]: Harwood, William (May 17, 2009). "Part of camera in newly repaired instrument revived". *Spaceflight Now*. Archived from the original on May 20, 2009. Retrieved May 17, 2009.

[^255]: Gutro, Rob (January 17, 2019). "Hubble's Wide Field Camera 3 Recovered, Collecting Science Data". NASA. Archived from the original on January 11, 2019. Retrieved January 13, 2019.

[^256]: Kornfeld, Laurel (January 17, 2019). "Hubble's Wide Field Camera 3 resumes operations". *Spaceflight Insider*. Archived from the original on February 9, 2019. Retrieved February 9, 2019.

[^257]: "NASA Continues Work on Hubble Space Telescope – Backup Computer Turned On, but It Fails With the Same Error". *SciTechDaily*. June 26, 2021. Archived from the original on June 26, 2021. Retrieved June 26, 2021.

[^258]: Mathewson, Samantha (June 28, 2021). "No quick fix for Hubble Space Telescope's computer glitch, NASA says". *Space.com*. Archived from the original on July 15, 2022. Retrieved October 15, 2023.

[^259]: Dunn, Marcia (June 16, 2021). "Computer trouble hits Hubble Space Telescope, science halted". *AP NEWS*. Archived from the original on June 16, 2021. Retrieved June 20, 2021.

[^260]: Jenner, Lynn (June 16, 2021). "Operations Underway to Restore Payload Computer on NASA's Hubble". *NASA*. Archived from the original on June 20, 2021. Retrieved June 20, 2021.

[^261]: "NASA Returns Hubble Space Telescope to Science Operations – NASA". July 19, 2021. Archived from the original on October 23, 2023. Retrieved October 15, 2023.

[^262]: Chappell, Bill (July 16, 2021). "Hobbled Hubble Telescope Springs Back To Life On Its Backup System". *NPR*. Archived from the original on July 16, 2021. Retrieved July 16, 2021.

[^263]: Clery, Daniel (July 16, 2021). "'Hubble is back!' Famed space telescope has new lease on life after computer swap appears to fix glitch". *Science*. Archived from the original on October 21, 2021. Retrieved July 16, 2021.

[^264]: Hunt, Katie (July 19, 2021). "The Hubble Space Telescope is functioning again after more than month offline". *CNN*. Archived from the original on July 19, 2021. Retrieved July 19, 2021.

[^265]: "Hubble Instruments Remain in Safe Mode, NASA Team Investigating". *HubbleSite.org*. Space Telescope Science Institute. November 4, 2021. Archived from the original on November 24, 2021. Retrieved November 24, 2021.

[^266]: "Hubble Space Telescope team revives powerful camera instrument after glitch". *Space.com*. November 22, 2021. Archived from the original on November 23, 2021. Retrieved November 24, 2021.

[^267]: Adkins, Jamie (December 8, 2021). "NASA Returns Hubble to Full Science Operations". *NASA*. Archived from the original on December 7, 2021. Retrieved December 8, 2021.

[^268]: Whitehouse, David (January 17, 2004). "Why Hubble is being dropped". *BBC News*. Archived from the original on June 14, 2017. Retrieved January 10, 2007.

[^269]: Wall, Mike (April 24, 2015). "How Will the Hubble Space Telescope Die?". *Space.com*. Archived from the original on May 5, 2017. Retrieved May 16, 2017.

[^270]: Northon, Karen (June 23, 2016). "NASA Extends Hubble Space Telescope Science Operations Contract" (Press release). NASA. Archived from the original on June 26, 2016. Retrieved June 26, 2016.

[^271]: Adkins, Jamie (November 16, 2021). "NASA Extends Hubble Operations Contract, Provides Mission Update" (Press release). NASA. Archived from the original on March 17, 2022. Retrieved June 19, 2022.

[^272]: Cowing, Keith (July 22, 2005). "NASA Considering Deletion of Hubble Deorbit Module". SpaceRef. Retrieved January 10, 2007.

[^273]: "Servicing Missions". *HubbleSite.org*. Space Telescope Science Institute. Archived from the original on April 9, 2022. Retrieved April 7, 2022.

[^274]: Bennett, Jay (February 14, 2017). "A New Spaceship Could Fly Astronauts to the Hubble Space Telescope for Repairs". *Popular Mechanics*. Archived from the original on February 14, 2017. Retrieved February 15, 2017.

[^275]: Foust, Jeff (June 15, 2020). "Hugging Hubble longer". *The Space Review*. Archived from the original on June 16, 2020. Retrieved June 16, 2020.

[^276]: Greenfieldboyce, Nell (May 16, 2024). "Private mission to save the Hubble Space Telescope raises concerns, NASA emails show". *NPR*. Retrieved May 22, 2024.

[^277]: Garner, Rob (September 29, 2022). "NASA, SpaceX to Study Hubble Telescope Reboost Possibility". *nasa.gov*. Archived from the original on November 3, 2022. Retrieved November 6, 2022.

[^278]: "NASA May Let Billionaire Astronaut and SpaceX Lift Hubble Telescope (Published 2022)". *The New York Times*. September 30, 2022.

[^279]: "NASA, SpaceX to Study Hubble Telescope Reboost Possibility - NASA". December 22, 2022.

[^280]: Foust, Jeff (September 15, 2024). "Crew Dragon splashes down to conclude Polaris Dawn mission". *SpaceNews*. Retrieved November 24, 2024.

[^281]: Matson, John (May 8, 2009). "Last Dance with the Shuttle: What's in Store for the Final Hubble Servicing Mission". *Scientific American*. Archived from the original on December 26, 2010. Retrieved May 18, 2009.

[^282]: Berger, Brian (May 23, 2007). "NASA Adds Docking Capability For Next Space Observatory". Space.com. Archived from the original on February 4, 2019. Retrieved June 4, 2012.

[^283]: "NASA's Hubble Finds Most Distant Galaxy Candidate Ever Seen in Universe" (Press release). NASA. January 26, 2011. Archived from the original on May 2, 2017. Retrieved June 4, 2012. Visual representation Archived June 5, 2019, at the Wayback Machine.

[^284]: "ESA JWST Timeline". Sci.esa.int. June 30, 2003. Archived from the original on August 21, 2003. Retrieved June 4, 2012.

[^285]: "About Webb's Launch". NASA. Archived from the original on June 16, 2019. Retrieved November 4, 2006.

[^286]: "FAQ". *jwst.nasa.gov*. Archived from the original on July 23, 2019. Retrieved April 6, 2022.

[^287]: Amos, Jonathan (April 29, 2013). "Herschel space telescope finishes mission". *BBC News*. Archived from the original on February 21, 2019. Retrieved April 29, 2013.

[^288]: "JPL: Herschel Space Observatory: Related Missions". Herschel.jpl.nasa.gov. Archived from the original on December 3, 2016. Retrieved June 4, 2012.

[^289]: "What Will Astronomy Be Like in 35 Years?". *Astronomy*. August 2008.

[^290]: "LUVOIR Mission Concept Study Final Report". *luvoirtelescope.org*. NASA. August 26, 2019. Archived from the original on May 24, 2021. Retrieved May 24, 2021.

[^291]: Staff (November 4, 2021). "New Report Charts Path for Next Decade of Astronomy and Astrophysics; Recommends Future Ground and Space – Telescopes, Scientific Priorities, Investments in Scientific Community". *National Academies of Sciences, Engineering, and Medicine*. Archived from the original on November 5, 2021. Retrieved November 5, 2021.

[^292]: Fienberg, Richard Tresch (September 14, 2007). "Sharpening the 200-Inch". *Sky & Telescope*. Archived from the original on August 28, 2018. Retrieved July 1, 2008.

[^293]: Chow, Denise; Wu, Jiachuan (July 12, 2022). "Photos: How pictures from the Webb telescope compare to Hubble's - NASA's $10 billion telescope peers deeper into space than ever, revealing previously undetectable details in the cosmos". *NBC News*. Archived from the original on July 15, 2022. Retrieved July 23, 2022.

[^294]: Garner, Rob (July 11, 2022). "NASA's Webb Delivers Deepest Infrared Image of Universe Yet". *NASA*. Archived from the original on July 12, 2022. Retrieved July 23, 2022.

[^295]: Overbye, Dennis; Chang, Kenneth; Tankersley, Jim (July 11, 2022). "Biden and NASA Share First Webb Space Telescope Image – From the White House on Monday, humanity got its first glimpse of what the observatory in space has been seeing: a cluster of early galaxies". *The New York Times*. Archived from the original on July 12, 2022. Retrieved July 23, 2022.

[^296]: Pacucci, Fabio (July 15, 2022). "How Taking Pictures of 'Nothing' Changed Astronomy - Deep-field images of "empty" regions of the sky from Webb and other space telescopes are revealing more of the universe than we ever thought possible". *Scientific American*. Archived from the original on July 16, 2022. Retrieved July 23, 2022.