The Interdisciplinary Evolution of the Hubble Space Telescope

1. The Interdisciplinary Evolution of the Hubble Space Telescope An Historical Examination of Key Interdisciplinary Interactions Greg Carras, Jerry Cordaro, Andrew Daga, Sean Decker, Jack Kennedy, Susan Raizer University of North Dakota, Department of Space Studies 24 April 2006

2. The Hubble Space Telescope: An Overview • An orbiting telescope that collects light from celestial objects in visible, ultraviolet, and near-infrared wavelengths • Launched 24 April 1990 aboard the Space Shuttle Discovery • Dimensions: Cylindrical 24,500 lb (11,110-kg), 43 ft long (13.1 m ) and 14.1 ft (4.3m) wide • Orbital period: 96 minutes • Primarily powered by the sunlight collected by its two solar arrays • The telescope’s primary mirror is 2.4 m (8 ft) in diameter • Was created by NASA with substantial and continuing participation by ESA • Operated by the Space Telescope Science Institute (STSI) in Baltimore, MD • Named for Edwin Powell Hubble "The Hubble Space Telescope is the most productive telescope since Galileo's" - Robert Kirshner, President of the American Astronomical Society Reference: Image and data: STSI (www.hubblesite.org)

3. The evolution of HST may be best approached by understanding the interaction of four factors: The Historical Context (and the post WWII trend toward “Big Science”) The Social and Political Conditions The Technological Dimension The Participants (People and Agencies)

4. Hubble’s Historical Context • At the beginning of the 20th Century, scientists had a remarkably limited view of the physical universe – many believed that our galaxy was the only galaxy. • Before WWII most astronomy was conducted by individuals or small groups, and astronomical observatories were funded by private philanthropists (example: Carnegie) or by an individual astronomer (example: Percival Lowell). • By the 1920’s this view was being rapidly revised, in part due to the observations of Edwin Hubble and Milton Humason in the 20’s and 30’s who saw many other galaxies, and that these galaxies were moving away from each other (which leads to the concept of an expanding universe and the Hubble Constant). • During WWII, the federal government teamed up with industry and the scientific community to form working partnerships. People learned how to develop transformational projects quickly and “Big Science” is born. • Some scientists learn how to play the game and extend themselves to be activists for important programs. One of these, an astronomer, is Lyman Spitzer, Jr.

5. Hubble’s Historical Context (continued) • In 1946 Spitzer publishes “Astronomical Advantages of an Extra-Terrestrial Observatory,” for RAND. It lays out in detail for the first time the enormous advantages of a space-based telescope. This report remains classified for years. • The US Army has been experimenting with captured V2 rockets, some of which have been equipped with scientific payloads. • In 1950, at a dinner party in his home, physicist James Van Allen and several scientists consider the idea for a third International Polar Year – this will become the IGY. An increasing number of scientists are looking at the space environment and new space age technologies to further scientific exploration. • Other scientists and engineers are also speculating about the new realm of possibilities for science, including Wernher von Braun, who describes a manned orbital telescope in 1952. • 1955: In response to growing pressure from scientists, the US National Academy of Sciences and National Science Foundation jointly agree to seek approval to orbit a scientific satellite during the upcoming IGY (to be 1957-1958). • During this period, many scientists remain unconvinced of the idea to take science into space. Nevertheless a scientific advocacy emerges, and it learns to become politically savvy. The paradigm has shifted to Big Science.

6. Hubble’s Historical Context (continued) • In 1958 (and following Sputnik), the Space Science Board of National Academy of Sciences calls for and receives hundreds of suggestions for follow-on projects to IGY. • These are forwarded to NASA's Space Science Working Group on "Orbital Astronomical Observatories (OAOs)" President Eisenhower enthusiastically supports. • In the Cold War climate, NASA is interested in demonstrating what it can do. In 1960-61 it issues first RFP’s for OAO series. • The contentious relationship between NASA and the science community takes form with the OAO project. Scientists who have been used to taking complete charge of their science projects will now have to contend with a loss of control to NASA. • On the positive side: With OAO, the idea of a Guest Observer is introduced – breaking from the idea of strict control by a single Principal Investigator. This will have later implications as key scientists will insist that the new Large Telescope be a National Facility (open to all) • On the negative side: 2 of 4 OAO missions fail – in large part because NASA did not communicate well with the scientists and the technology was too complicated. Reference: Smith, Robert W, et al. The Space Telescope: A Study of NASA, Science, Technology, and Politics. New York: Cambridge Univ. Press, 1989

7. Social and Political Conditions • As NASA begins to seriously contemplate a Large Space Telescope, the financial and budgetary condition of the nation weighs heavily. This factor, and how the various participants perceive it, will prove to be critical in defining Hubble’s scientific potential, management, ultimate cost, and schedule. • By the mid-1970’s the federal budget has been overstressed by the expenses of war and the Great Society programs, and the economy is stagnating. • NASA senior management is concentrating on the new Space Shuttle and the political climate for new expensive projects is hostile. • NASA continues to pursue an LST by using available funds (not needing congressional approval) to fund “Phase A” studies, forcing Marshall Space Flight Center to compete with Goddard Space Flight Center to become the lead center. • NASA Administrator Fletcher finds the Phase A cost estimates politically untenable – and orders MSFC to limit the program cost to $300M. • Finally, throughout the 1960’s and 70’s, the DoD has been building a series of increasingly sophisticated reconnaissance satellites, and it forces controls on NASA that severely limit NASA’s access to the technology to protect secrecy. Ironically, the same companies that know how to build the recon satellites are ultimately selected to build Hubble. Reference: Smith, Robert W, et al. The Space Telescope: A Study of NASA, Science, Technology, and Politics. New York: Cambridge Univ. Press, 1989

8. Hubble’s Participants – Key People and Agencies The four key participants in the development lifecycle of Hubble: • Space Agencies • NASA Headquarters – the Office of Space Science believes the LST is a major priority, but senior management were reluctant to propose any new program. • MSFC – it had no astronomy expertise and was threatened with closure at the time of the LST Phase A competition; it wanted the LST badly and said so. • GSFC – it had the experienced people and know-how to build astronomical sats (it was lead for OAO), but was overburdened with project work; it’s Director was ambivalent about the project. • JSC, KSC and JPL would play important roles in the program too. JSC’s astronauts would prove essential. JPL designed and built the WF/PC (and the $60M spare). • Astronomers and other scientists within NASA would play a pivotal role in coordinating with the science community, of these Dr Robert O’Dell (Chief Project Scientist at MSFC) and Dr Nancy Roman of NASA HQ were crucial. • ESA – It wanted a substantial space science program but could not do it on its own, and NASA needed to satisfy Congress while reassuring domestic scientists that they would not sacrifice control as a price for ESA’s involvement • Executive and Legislative Branches of Government • Executive Branch – despite budget constraints imposed by the Ford administration, the OMB and President Ford were generally supportive, as were officials in the Carter and Reagan administrations. • Congress – Hubble will face stiff opposition from key congressional committees forcing major delays and economic limits. Congress will ultimately mandate international cooperation. The most prominent opponents of Hubble were Representative Edward P. Boland (D-MA) and Senator William Proxmire (D-WI). Reference: Smith, Robert W, et al. The Space Telescope: A Study of NASA, Science, Technology, and Politics. New York: Cambridge Univ. Press, 1989

9. Key People and Agencies (continued) • Scientists and Advocates • Individual scientists will come to save the telescope by rallying their community and aggressively lobbying congress. • Of these, the most influential will be Lyman Spitzer and John Bahcall, both of Princeton. Their collaboration with Robert O’Dell (at MSFC) in lobbying Congress will come to be called the “Princeton-Huntsville Axis.” O’Dell actively promotes the project in scientific journals and presentations. • Industry • Many companies contributed to LST/HST, including all major aerospace firms, most in subcontractor roles to Lockheed Missiles and Space Company (CA) for the SSM, and to Perkin-Elmer (CT) for the OTA. • Lockheed and P-E had substantial experience working on highly classified PHOTOINT satellites. • Other firms were contracted by the universities to build elements of the Scientific Instruments. • At various times, corporate competitors worked together and with NASA and outside scientists to lobby congress at critical junctures. • Importantly, since both Lockheed and P-E were operating as “associate contractors” – no company was fully charged with systems engineering authority, and NASA was unable to perform this role adequately. Reference: Smith, Robert W, et al. The Space Telescope: A Study of NASA, Science, Technology, and Politics. New York: Cambridge Univ. Press, 1989

10. Hubble’s Evolution – Consolidated Summary • In the context of big science and Cold War tensions and technology advancements, NASA and the scientific community find common purpose in proposing a large (3m) reflecting telescope in Earth orbit. Astronomers know it will be revolutionary; NASA and several presidents agree. • As Apollo concludes, NASA is under fire and fighting to keep field centers open. It develops an LST program but forces GSFC to compete with MSFC to lead the program. The compromise sets up antagonism between the centers. • With Marshall in the lead, the program is believed to be untenable politically – an artificial limit of $300M is imposed, and the DoD demands limits on contractor penetration of the two key defense contractors. • With constant cost overages, NASA management demands reductions, forcing trade-off studies of capability versus cost. In this process the 3m primary mirror will be reduced to 2.4m. The scientists are always pushing back. • When the program is proposed to Congress, the House appropriations subcommittee rejects it, forcing NASA to appeal to the Senate in hopes of effectuating a resolution, and NASA considers holding off on the program. • It is at this point that university scientists, key NASA staffers and scientists, and contractors, begin to collaborate to lobby congress. • From this emerges a partial victory, leading to the restoration of some funding and the mandate that NASA collaborate with ESA. NASA begins talks with ESA.

11. Hubble’s Evolution – Consolidated Summary • As the program moves into the design and development phase (C/D), a manpower cap and the limited budget restrain Marshall’s ability to manage the program. NASA depends on two associate contractors to do their own systems engineering. MSFC saw itself in this role, but was not able to do it. • During this period the relationship between MSFC and GSFC is antagonistic and even hostile. Goddard is charged with developing the scientific instruments and eventually operating the telescope, but only reluctantly takes direction from MSFC. Marshall objects to Goddard’s interference, and Marshall’s project scientist (O’Dell) takes the initiative away from GSFC. • As the project moves ahead, even with ESA’s 15% contribution, the LST runs out of money. Faced with the prospect of severely reducing the scientific capability and delaying the launch, NASA management concedes to extend the launch date and returns to congress for more money. • Status 1980: From it’s inception, LST has been underfunded and consequently, its capabilities were oversold (Smith, 1989). In 1980, the program is in crisis but still at a design stage where NASA considers cutting back on certain technologies to save money. • During this time, scientists are working to create the methodologies that will be needed to operate HST at the STSI. A entire new star reference system is created to help guide the telescope. • In 1983, the program hits another crisis – NASA finally recognizes that changes need to be made, the launch date extended, and NASA HQ demands new managers and appoints its own project manager. NASA works with OMB and Congress begins to infuse much more money. Things begin to change.

12. Hubble’s Evolution – Consolidated Summary • Between 1983 and 1986, the program is disciplined and turned around. New managers at NASA do not feel tied to the unrealistic promises that the program has made. Launch is scheduled for 1986. • In 1986, just as the program is being readied for its final round of thermal-vacuum chamber testing, the Shuttle fleet is grounded with the Challenger disaster. NASA is afraid to lose the technical skills it needs to finish the program, so work continues to fix lingering problems and complete the thermal-vacuum testing. HST goes into protected storage. • In 1990, HST is launched and very quickly put into service. Soon, it will be discovered that there is a flaw in the optics, which will be traced to a manufacturing error at P-E (which P-E knew about for 10 years). • In 1993, in a dramatic series of EVA’s during the first servicing mission (SM), HST’s optics are corrected and a new era of space astronomy finally begins. • Since 1993, there have been 3 additional SM’s, each one replacing and upgrading HST to state-of-the-art technology. Hubble has generated data of unprecedented quality in vast quantities since – and continues to do so. With more demand for observing time than can be filled, and the ability to be extended indefinitely, Hubble has turned out to be everything and more than its supporters ever claimed. References: Smith, Robert W, et al. The Space Telescope: A Study of NASA, Science, Technology, and Politics. New York: Cambridge Univ. Press, 1989, and personal interview, Dr David Leckrone, Goddard Space Flight Center, 10 April 2006.

13. Hubble’s Technological Dimension • The Hubble Space Telescope was designed with many constraints – both technical and cost. • This technology section will cover the technology components of Hubble and the rationale that drove decisions on its design. Index to Technology Slides Hubble Components - Overall Components - Power Systems - Spacecraft Systems - Mirrors and Baffles – Mirror Problem - Sensors - Actuators - Scientific Instruments Most Difficult Technical Challenge – Pointing Control System “Get the Cost Down” Initial Deployment Components and Servicing Missions

14. Hubble Technology Overall Components – Exploded View

15. Hubble Technology Power Systems Batteries:- 6 nickel-hydrogen (NiH) batteries- Power storage capacity is equal to 20 car batteries- Power usage: 2,800 watts Solar Arrays: (2) 40-foot (12-meter) panels that convert sunlight into 2400 watts of electricity in order to power the telescope.

16. Hubble Technology Power Systems http://hubble.nasa.gov/technology/summary.php

17. Hubble Technology Spacecraft Systems Communications antennae (2) Transmit Hubble's information to communications satellites called the Tracking & Data Relay Satellite System (TDRSS) for relay to ground controllers at the Space Telescope Operations Control Center (STOCC) in Greenbelt, Maryland. Computer support systems modules Contains devices and systems needed to operate the Hubble Telescope. Serves as the master control system for communications, navigation, power management, etc. Electronic boxes Houses much of the electronics including computer equipment and rechargeable batteries. Aperture door Protects Hubble's optics in the same way a camera's lens cap shields the lens. It closes when Hubble is not in operation to prevent bright light from hitting the mirrors and instruments. Light shield Light passes through this shaft before entering the optics system. It blocks surrounding light from entering Hubble. Pointing control system This system aligns the spacecraft to point to and remain locked on any target. The telescope is able to lock onto a target without deviating more than 7/1000th of an arcsecond, or about the width of a human hair seen at a distance of 1 mile.

18. Hubble Technology Spacecraft Systems

19. Hubble Technology Spacecraft Systems

20. Hubble Technology Spacecraft Systems

21. Hubble Technology Spacecraft Systems

22. Hubble’s Spacecraft Systems – the OTA

23. Hubble Technology Communications Hubble data path to the Goddard Space Flight Center.

24. Hubble Technology Pointing Control System The Pointing Control System (PCS) aligns Hubble so that the telescope points to and remains locked on a target. The PCS is designed for pointing to within .01 arcsec and is capable of holding a target for up to 24 hours while Hubble continues to orbit the Earth at 17,500 mph. If the telescope were in Los Angeles, it could hold a beam of light on a dime in San Francisco without the beam straying from the coin's diameter.

25. Hubble Technology Mirror and Baffles • Primary Mirror • Primary Mirror Diameter: 94.5 in (2.4 m), Weight: 1,825 lb (828 kg). • Hubble's two mirrors were ground so that they do not deviate from a perfect curve by more than 1/800,000ths of an inch. If Hubble’s primary mirror were scaled up to the diameter of the Earth, the biggest bump would be only six inches tall. • Secondary Mirror • Secondary Mirror Diameter: 12 in (0.3 m), Weight: 27.4 lb (12.3 kg). • Focal Plane • Mirrors focus starlight on the Focal Plane. • Baffles: • Keep out stray light. • Main baffle • Central baffle • Secondary mirror baffle The telescope's primary mirror (2.4 m diameter) being hoisted up

26. Hubble Technology Mirror and Baffles Hubble Main Mirror Workers study Hubble’s main, eight-foot (2.4 m) mirror. Hubble, like all telescopes, plays a kind of pinball game with light to force it to go where scientists need it to go. When light enters Hubble, it reflects off the main mirror and strikes a second, smaller mirror. The light bounces back again, this time through a two-foot (0.6 m) hole in the center of the main mirror, beyond which Hubble’s science instruments wait to capture it. In this photo, the hole is covered up.

27. Hubble Technology Mirror and Baffles

28. Hubble Technology Mirror and Baffles

29. Hubble Technology Mirror and Baffles

30. Hubble Technology Mirror and Baffles Mirror Problem The mission controllers made progress and by 21 May began receiving the first optical images from the telescope. These views of a double star in the Carina system, scientists believed, were much clearer than those from ground-based telescopes. Such success left project officials surprised on the weekend of 23–24 June when the telescope failed a focus test. The controllers had moved the telescope’s secondary mirror to focus the light, but a hazy ring or “halo” encircled the best images. Subsequent tests determined that the blurry images resulted from the “spherical aberration” of the primary mirror; spherical aberration reflected light to several focal points rather than to one. It occurred because Perkin-Elmer had removed too much glass, polishing it too flat by 1/50th of the width of a human hair. This seemingly slight mistake, however, prevented the telescope from making sharp images.

31. Hubble Technology Mirror and Baffles COSTAR Corrective Optics Space Telescope Axial Replacement Although the primary mirror was not one of the replaceable units, its aberration could be corrected, much like the way an eye doctor corrects poor vision with spectacles, by modifications to “second generation” scientific instruments. COSTAR, the corrective optics Space Telescope axial replacement, would replace the high speed photometer and use relay mirrors mounted on movable arms to focus the scattered light.

32. Hubble Technology Optical Camera Channel and Baffles Four Optical Camera Channel and Baffle assemblies from the Wide Field and Planetary Camera (WF/PC) 1 recovered from the Hubble Space Telescope during HST Service Mission

33. Hubble Technology Optical Camera Channel and Baffles Faint Object Camera (FOC) M1 Field Mirror Mechanism that was ultimately installed as part of the COSTAR (Corrective Optics Space Telescope Axial Replacement) payload during Space Shuttle Mission STS-61 (Hubble Service Mission 1) to correct errors in the primary mirror onboard the Hubble Space Telescope. The error was the result of a residual aberration polished into the primary due to a mis-assembled nulling apparatus; the error resulted in the Hubble's primary mirror being ground about 2 micrometers too flat (1/40 the thickness of a human hair). Scientists and engineers devised COSTAR with four small mirrors, about the size of dimes and quarters. The small mirrors were intentionally produced with a flaw identical to and opposite the flaw on the primary Hubble mirror.

34. Hubble Technology Sensors Fine Guidance Sensors (3) These sensors are locked onto two guide stars to keep Hubble in the same relative position of these stars. Coarse Sun Sensors (2) Measure Hubble's orientation to the sun. Also assist in deciding when to open and close the aperture door. Magnetic Sensing System Measure Hubble position relative to Earth's magnetic field. Rate Sensor Unit Two rate sensing gyroscopes measure the attitude rate motion about its sensitive axis. Fixed Head Star trackers An electro-optical detector that locates and tracks a specific star within its field of view.

35. Hubble Technology Actuators Reaction Wheel Actuators (4) The reaction wheels work by rotating a large flywheel up to 3000 rpm or braking it to exchange momentum with the spacecraft which will make Hubble turn. Magnetic Torquers (4) The torquers are used primarily to manage reaction wheel speed. Reacting against Earth's magnetic field, the torquers reduce the reaction wheel speed, thus managing angular momentum.

36. Hubble Technology Actuators

37. Hubble Technology Scientific Instruments Axial bays (4) Four instruments are aligned with the main optical axis and are mounted just behind the primary mirror. As of the year 2000 they consisted of: ACS (Advanced Camera for Surveys) The newest camera (2002) with a wider field of view, and better light sensitivity. It effectively increases Hubble's discovery power by 10x. NICMOS (Near Infrared Camera and Multi-Object Spectrometer) Infrared instrument that is able to see through interstellar gas and dust. STIS (Space Telescope Imaging Spectrograph) Separates light into component wavelengths, much like a prism. COSTAR Contains corrective optics for spherical aberration in the primary mirror. Radial bay (1) Wide Field/Planetary Camera 2 (WFPC2) is housed here. Taking images that most resemble human visual information, WFPC2 is responsible for taking nearly all of Hubble's famous pictures. Fine guidance sensors (3) The sensors lock onto guide stars and measure relative positions, providing data to the spacecraft's targeting system and gathering knowledge on the distance and motions of stars.

38. Hubble Technology Scientific Instruments

39. Hubble Technology Scientific Instruments Space Telescope Imaging Spectrograph (STIS) Engineers in a clean room at Ball Aerospace in Boulder, Colo., work on one of Hubble’s instruments, the Space Telescope Imaging Spectrograph (STIS), in 1996. The instrument, installed in Hubble in 1997, breaks light into colors, giving scientists an important analytical tool for studying the cosmos. STIS has been used to study such objects as black holes, new stars, and massive planets forming outside our solar system.

40. Hubble Technology The Most Difficult Technical Challenge – Pointing Control System The Problem: A major problem for NASA and its contractors was the means to guide and stabilize the telescope. If the completed telescope was to perform to the negotiated requirements, it would have to be capable of being aimed at an astronomical target with a pointing stability of 0.005 seconds of arc, an angle on the sky about 360,000 times smaller than the angle that is subtended by the diameter of the full moon. So taxing was this requirement that it was widely viewed in NASA and outside as the most difficult technical challenge the designers and builders had to overcome. The telescope not only had to be pointed extremely accurately, means also had to be devised to keep it locked on its astronomical targets. This task was crucial because there would inevitably be tiny disturbances that would act to move the spacecraft away from its targets, disturbances known as "jitter". Jitter might arise from the motions of the gyroscopes in pointing, for example. Should the entire spacecraft be moved if small corrections in its position were needed (a method known as body pointing)? Or should the secondary mirror of the Large Space Telescope be shifted to compensate for the spacecraft's minor motions (a method known as image motion compensation)?

41. Hubble Technology The Most Difficult Technical Challenge – Pointing Control System The Answer: During Phase A, Bendix had performed studies for Marshall that argued that body pointing alone was sufficient. Marshall, however, was not convinced. Hence the center's Phase A design concept also incorporated a movable secondary mirror. But more studies persuaded Marshall that control moment gyroscopes could point and stabilize the telescope. If so, a moving secondary would not be essential, even though Perkin-Elmer argued that it promised to give the best performance. Marshall's basic engineering approach was to use the simplest available systems where possible, and for pointing and control that would mean using eithercontrol moment gyroscopes or reaction wheels alone, but preferably not the two in combination.

42. Hubble Technology “Get the Cost Down” The Problem: Financial pressure pushed the Center’s design activities and often forced it to relinquish conservative engineering principles. The Center’s March 1972 project plan called for three telescopes, an engineering model, a “precursor” flight unit, and the final LST. Design and development would cost between $570 and $715 million. Headquarters believed this was too expensive. In a December 1972 meeting, NASA Administrator Fletcher “emphasized that the current NASA fiscal climate was not conducive to initiation of large projects” and suggested $300 million as a cost target.

43. Hubble Technology “Get the Cost Down” A “proto-flight” approach would eliminate the engineering and precursor units; a single spacecraft would serve as test model and flight unit. The proto-flight approach had been successfully tried for Department of Defense projects, and the Center expected it to reduce costs—which would please Congress—and speed progress to operations—which would please the astronomers. The telescope maintenance strategy also changed. Rather than designing for extensive repair in orbit inside a pressurized cabin, Marshall suggested a design that would eliminate the cabin and minimize repairs in orbit. The new design assumed the Space Shuttle could return the telescope to Earth for major repairs. These changes simplified the overall LST design and development scheme.

44. Hubble Technology “Get the Cost Down” By December 1974 the Program Development task team had downsized the telescope. As before the team had to balance cost and performance and devise a design pleasing to Congress and the astronomers. Team leader Downey said the Agency wanted “to procure the lowest cost system that will provide acceptable performance” and would “be willing to trade performance for cost.” Working with the LST science groups and contractors, the team reduced the telescope’s primary mirror from a 3-meter aperture to 2.4 meters. This major change mainly resulted from new NASA estimates of the Space Shuttle’s payload delivery capability; the Shuttle could not lift a 3-meter telescope to the required orbit. In addition, changing to a 2.4-meter mirror would lessen fabrication costs by using manufacturing technologies developed for military spy satellites. The smaller mirror would also abbreviate polishing time from 3.5 years to 2.5 years. The redesign also reduced the mass of the support systems module from 24,000 pounds to 17,000 pounds; the SSM moved from the aft of the spacecraft to one-third of the way forward and became a doughnut around the primary mirror. These changes diminished inertia and facilitated steering of the spacecraft, thus permitting a smaller pointing control system. The astronomers chose to reduce the number of scientific instruments from seven to four. Finally, the Marshall team believed that designing for repair would allow for lower quality standards.

45. Hubble Technology Initial Deployment Components and Servicing Missions 1990 Initial Complement at Deployment: WFPC (1) - Wide Field/Planetary Camera - First-generation imaging camera. WFPC (1) operated in either Wide Field mode, capturing the largest images, or Planetary mode with higher resolution. GHRS - Goddard High Resolution Spectrograph - First-generation spectrograph. GHRS was used to obtain high resolution spectra of bright targets. FOS - Faint Object Spectrometer - First-generation spectrometer. FOS was used to obtain spectra of very faint or faraway sources. FOS also had a polarimeter for the study of the polarized light from these sources. FOC - Faint Object Camera - First-generation imaging camera. FOC is used to image very small field of view, very faint targets. This is the final, first-generation instrument still on Hubble. HSP - High Speed Photometer - First-generation photometer. This instrument was used to measure very fast brightness changes in diverse objects, such as pulsars. FGS - Fine Guidance Sensors - Science/guidance instruments. The FGS's are used in a "dual-purpose" mode serving to lock on to "guide stars" which help the telescope obtain the exceedingly accurate pointing necessary for observation of astronomical targets. These instruments can also be used to obtain highly accurate measurements of stellar positions.

46. Hubble Technology Initial Deployment Components and Servicing Missions • 1993 Servicing Mission 1: • WFPC2 - Wide Field Planetary Camera 2 - Second-generation imaging camera. WFPC2 is an upgraded version of WF/PC (1) which includes corrective optics and improved detectors. • COSTAR - Corrective Optics Space Telescope Axial Replacement - Second-generation corrective optics. COSTAR is not an actual instrument. It consists of mirrors which refocus the abbreviated light from Hubble's optical system for first-generation instruments. Only FOC utilizes its services today. • Restoring Hubble's Vision • As the first in a series of planned visits to the orbiting Hubble Space Telescope, the First Servicing Mission (STS-61) in December 1993 had a lot to prove and a lot to do. The mission's most important objective was to install two devices to fix Hubble's vision problem. Because Hubble's primary mirror was incorrectly shaped, the telescope could not focus all the light from an object to a single sharp point. Instead, it saw a fuzzy halo around objects it observed. • Once astronauts from the space shuttle Endeavour caught up with the orbiting telescope, they hauled it into the shuttle's cargo bay and spent five days tuning it up. They installed two new devices—the Wide Field and Planetary Camera 2 (WFPC2) and the Corrective Optics Space Telescope Axial Replacement (COSTAR). Both WFPC2 and the COSTAR apparatus were designed to compensate for the primary mirror's incorrect shape. • Also installed during the First Servicing Mission were: • New solar arrays to reduce the "jitter" caused by excessive flexing of the solar panels during the telescope's orbital transition from cold darkness into warm daylight • New gyroscopes to help point and track the telescope, along with fuse plugs and electronic units. • This successful mission not only improved Hubble's vision — which led to a string of remarkable discoveries in a very short time — but it also validated the effectiveness of on-orbit servicing.

47. Hubble Technology Initial Deployment Components and Servicing Missions Servicing Mission 2: STIS - Space Telescope Imaging Spectrograph - Second-generation imager/spectrograph. STIS is used to obtain high resolution spectra of resolved objects. STIS has the special ability to simultaneously obtain spectra from many different points along a target. NICMOS - Near Infrared Camera/Multi-Object Spectrometer - Second-generation imager/spectrograph. NICMOS is Hubble's only near-infrared (NIR) instrument. To be sensitive in the NIR, NICMOS must operate at a very low temperature, requiring sophisticated coolers. Problems with the solid nitrogen refrigerant have necessitated the installation of the NICMOS Cryocooler (NCC) on SM3B to continue its operation. The light from the most distant galaxies is shifted to infrared wavelengths by the expanding universe. To see these galaxies, Hubble needed to be fitted with an instrument that could observe infrared light. During the 10-day Second Servicing Mission (STS-82) in February 1997, the seven astronauts aboard the space shuttle Discovery installed two technologically advanced instruments. The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) would be able to observe the universe in the infrared wavelengths. The second instrument—the versatile Space Telescope Imaging Spectrograph (STIS)—would be used to take detailed pictures of celestial objects and to hunt for black holes. Both instruments had optics that corrected for the flawed primary mirror. In addition, they featured technology that wasn't available when scientists designed and built the original Hubble instruments in the late 1970s—and opened up a broader viewing window for Hubble. The new instruments replaced the Goddard High Resolution Spectrograph and the Faint Object Spectrograph. Also installed during the Second Servicing Mission were: • A refurbished Fine Guidance Sensor—one of three essential instruments used to provide pointing information for the spacecraft, to keep it pointing on target, and to calculate celestial distances • A Solid State Recorder (SSR) to replace one of Hubble's data recorders (An SSR is more flexible and can store 10 times more data) • A refurbished, spare Reaction Wheel Assembly—part of the Pointing Control Subsystem.

48. Hubble Technology Initial Deployment Components and Servicing Missions Servicing Mission 3a: On December 19, 1999, seven astronauts boarded the space shuttle Discovery to pay the Hubble Space Telescope a special holiday visit. After a successful launch and several trips around Earth, the crew caught up with Hubble and hauled it into the shuttle's cargo bay. Six days and three 6-hour spacewalks later, the crew had successfully completed Part A of the two-part Third Servicing Mission, which had them replacing worn or outdated equipment and performing several critical maintenance upgrades. Servicing Mission 3A (STS-103) was a busy one. The most pressing task was the replacement of gyroscopes, which accurately point the telescope at celestial targets. The crew, two of whom were Hubble repair veterans, replaced all six gyroscopes-as well as one of Hubble's three fine guidance sensors (which allow fine pointing and keep Hubble stable during observations) and a transmitter. The astronauts also installed an advanced central computer, a digital data recorder, an electronics enhancement kit, battery improvement kits, and new outer layers of thermal protection. Hubble was as good as new.

49. Hubble Technology Initial Deployment Components and Servicing Missions Servicing Mission 3b: On March 1, 2002, NASA launched the space shuttle Columbia into an orbit 360 miles above Earth, where its seven-member crew met with the Hubble Space Telescope to perform a series of upgrades. Servicing Mission 3B, also known as STS-109, was the fourth visit to Hubble. NASA split the original Servicing Mission 3 into two parts and conducted the first part – Servicing Mission 3A – in December 1999. The highly-trained astronauts performed five spacewalks. Their principal task was to install a new science instrument called the Advanced Camera for Surveys, or ACS. The first new instrument to be installed in Hubble since 1997, ACS brought the nearly 12-year-old telescope into the 21st century. With its wide field of view, sharp image quality, and enhanced sensitivity, ACS doubled Hubble’s field of view and collects data ten times faster than the Wide Field and Planetary Camera 2, the telescope’s earlier surveying instrument. Hubble gets its power from four large flexible solar array panels. The 8-year-old panels were replaced with smaller rigid ones that produce 30 percent more power. Astronauts also replaced the outdated Power Control Unit, which distributes electricity from the solar arrays and batteries to other parts of the telescope. Replacing the original unit, which has been on the job for nearly 12 years, required the telescope to be completely powered down for the first time since its launch in 1990. Reaction Wheel Assembly: Four Reaction Wheel Assemblies like this one are needed to point the telescope. Astronauts will replace one of them. During the last spacewalk astronauts installed a new cooling system for the Near Infrared Camera and Multi-Object Spectrometer, or NICMOS, which became inactive in 1999 when it depleted the 230-pound block of nitrogen ice that had cooled it since 1997. The new refrigeration system, which works much like a household refrigerator, chills NICMOS’s infrared detectors to below –315° F (–193° C). NICMOS Cooling System: An experimental refrigeration technology will make it possible to restore Hubble's infrared vision. New Steering Equipment: Astronauts replaced one of the four reaction wheel assemblies that make up Hubble's pointing control system. Flight software commands the reaction wheels to “steer” the telescope by spinning in one direction, which causes Hubble to spin in the other direction.

50. The Science of HubbleIt is not even remotely possible to cover all the science that Hubble has done in a single presentation. Tens of thousands of papers and hundreds of books have been written based on HST data, and every day generates 20 GB of data. Astronomers will be mining this resource for generations to come.