5
The Stratospheric Observatory for Infrared Astronomy

5.1
INTRODUCTION

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is included in this report at the request of the House Science and Technology Committee staff. SOFIA is currently funded under a NASA mission budget line and is not under an airborne science budget line. Upon completion of its development phase, SOFIA will become a suborbital airborne platform for infrared (IR) astronomy. SOFIA will continue the rich heritage of scientific achievement by the former Kuiper Airborne Observatory (KAO).

SOFIA is a partnership between NASA and the German Space Agency, Deutsches Zentrum fur Luft-und Raumfahrt, to develop and operate a Boeing 747 SP aircraft (see Figure 5.1) outfitted with a 2.5-meter Cassegrain reflecting telescope. When complete, SOFIA will have the largest airborne telescope in the world.

The German-built 2.5-meter telescope has been embedded in a specially modified Boeing 747 SP wide-body aircraft. The telescope is designed for infrared astronomy and will make observations aboard the aircraft while flying at altitudes above 41,000 feet. The observatory will get above 99 percent of the atmospheric water vapor and other infrared-absorbing gases, opening up windows to the universe not available from the ground.

The SOFIA Observatory concept embodies a number of key advantages that provide special advantages for astronomy in the coming decades:

  • SOFIA is a near-space observatory that comes home after every flight. Its scientific instruments can be exchanged regularly for repairs, to accommodate changing science requirements, and to incorporate new technologies. These instruments do not need to be space qualified.

  • Unlike a ground-based telescope or an orbiting spacecraft, SOFIA has unique capabilities for studying transient events. The observatory can operate on short notice from airbases worldwide, in both the northern and southern hemispheres, to respond to new scientific opportunities.

  • SOFIA’s diverse range of instrumentation will facilitate a coordinated program of analysis of specific targets and science questions. SOFIA’s 20-year design life time will enable long-term studies and follow-up of work initiated by SOFIA itself and by other observatories, such as the Hubble Space Telescope, Chandra, Spitzer, SMA, and ASTRO-F, as well as future facilities.

  • SOFIA will present an ideal venue in which to educate students, where they can participate in hands-on, cutting-edge space technology developments.



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5 The Stratospheric Observatory for Infrared Astronomy 5.1 INTRODuCTION The Stratospheric Observatory for Infrared Astronomy (SOFIA) is included in this report at the request of the House Science and Technology Committee staff. SOFIA is currently funded under a NASA mission budget line and is not under an airborne science budget line. Upon completion of its development phase, SOFIA will become a suborbital airborne platform for infrared (IR) astronomy. SOFIA will continue the rich heritage of scientific achievement by the former Kuiper Airborne Observatory (KAO). SOFIA is a partnership between NASA and the German Space Agency, Deutsches Zentrum fur Luft-und Raumfahrt, to develop and operate a Boeing 747 SP aircraft (see Figure 5.1) outfitted with a 2.5-meter Cassegrain reflecting telescope. When complete, SOFIA will have the largest airborne telescope in the world. The German-built 2.5-meter telescope has been embedded in a specially modified Boeing 747 SP wide-body aircraft. The telescope is designed for infrared astronomy and will make observations aboard the aircraft while flying at altitudes above 41,000 feet. The observatory will get above 99 percent of the atmospheric water vapor and other infrared-absorbing gases, opening up windows to the universe not available from the ground. The SOFIA Observatory concept embodies a number of key advantages that provide special advantages for astronomy in the coming decades: • SOFIA is a near-space observatory that comes home after every flight. Its scientific instruments can be exchanged regularly for repairs, to accommodate changing science requirements, and to incorporate new technolo - gies. These instruments do not need to be space qualified. • Unlike a ground-based telescope or an orbiting spacecraft, SOFIA has unique capabilities for studying transient events. The observatory can operate on short notice from airbases worldwide, in both the northern and southern hemispheres, to respond to new scientific opportunities. • SOFIA’s diverse range of instrumentation will facilitate a coordinated program of analysis of specific targets and science questions. SOFIA’s 20-year design life time will enable long-term studies and follow-up of work initiated by SOFIA itself and by other observatories, such as the Hubble Space Telescope, Chandra, Spitzer, SMA, and ASTRO-F, as well as future facilities. • SOFIA will present an ideal venue in which to educate students, where they can participate in hands-on, cutting-edge space technology developments. 

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 THE STRATOSPHERIC OBSERVATORY FOR INFRARED ASTRONOMY FIGURE 5.1 The modified 747 SP SOFIA aircraft. The telescope door aft of the wing was successfully tested in the fully open position shown here on December 18, 2009. SOURCE: Courtesy of NASA. • Because of its accessibility and ability to carry qualified non-crew members, SOFIA will include an education and public outreach (EPO) program, which is intended to be highly visible and designed to exploit the scientifically inspirational attributes of airborne astronomy. 5.2 STATuS The major aircraft structural modifications and the installation of the telescope were carried out at the L-3 Communications Integrated Systems facility in Waco, Texas. These modifications and installation of the telescope were completed with the following installation tasks still remaining: the telescope subsystems, mission control systems, and communications. Several check flights were conducted out of Waco, Texas, in 2007 and the aircraft was flown to the NASA Dryden Flight Research Center in late 2007. Further development of SOFIA is currently the responsibility of NASA Dryden, where the final installation and integration of its numerous operating and science-related systems will take place. In addition a multi-phase flight test program is currently ongoing. The first flight test phase focused on flying with the large external telescope cavity door closed. Following installation of an auxiliary power unit, insulation in the telescope cavity, and the first phase of the on-board Mission Control and Communications Systems, SOFIA will enter its second phase of flight testing, currently scheduled for late 2009 through the summer/fall of 2010. This phase will focus on the various aerodynamic and operational issues related to flying SOFIA at high altitudes at cruising speeds with the external telescope cavity door open. Concurrent with these aerodynamic test flights SOFIA will begin making its first astronomical science investiga - tions with a limited set of science instruments in a shared-risk arrangement. Following the completion of the first two flight-test phases, further upgrades to the aircraft avionics, comple - tion of the Mission Systems, and installation of the telescope cavity environmental control system will occur, followed by the checkout of the remaining suite of science instruments. These instrument commissioning flights, interspersed with observing opportunities for the general astronomical community, are planned for the years of 2011 through 2014. The full operations capability (FOC) milestone is scheduled to be achieved in late 2014. The full 960-hour annual science flight rate will be achieved within 3 years after the FOC date. Except during infrequent deployments, SOFIA will conduct its flight operations out of the Dryden Aircraft Operations Center located in Palmdale, California. SOFIA’s science operations are being planned jointly by Uni - versities Space Research Association (USRA) and the Deutsches SOFIA Institut (DSI) at the Science Mission Operations facility located at NASA’s Ames Research Center at Moffett Field near San Jose, California.

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0 REVITALIZING NASA’S SUBORBITAL PROGRAM 5.3 CAPABILITy The SOFIA aircraft will have an operational capability of more than 6 hours above 41,000 feet. The telescope has an effective aperture of 2.5 meters and a wavelength range of between 0.3 and 1,600 microns. The elevation range aboard the aircraft will be 20-60 degrees. The visible light image size will be better than 5.3-arc-second diameter (80 percent of encircled energy) at the focal plane. The telescope is diffraction-limited at wavelengths longer than 15 microns. There are eight first-generation science instruments being developed for SOFIA: six are U.S. instruments and two are German (Figure 5.2 and Table 5.1). Three U.S. instruments and one German instrument are destined to be facility-class instruments operated and maintained by the Science Mission Operations staff. The others are principal-investigator-class instruments that are operated and maintained by their development teams, although all SOFIA instruments are available for use in proposals by the general astronomical community. These first-generation instruments will cover wavelengths ranging from the visible into the microwave, with a mix of cameras and high- resolution spectrometers. SOFIA, like all airborne platforms, will provide enormous flexibility. SOFIA is planned to allow scientists the opportunity to improve or replace instrumentation so that the observa- tory will remain at the state of the art and continue to meet future scientific needs. SOFIA will be a platform for innovation where instrumentation can evolve with improvements in sensitivity, detector response time, observation technique, spectral resolution, and more. The SOFIA facility is designed for a 20-year operational life and will be capable of “Great Observatory”-class science. Once it begins operations in about 2011, SOFIA’s 2.5-meter (100-inch)-diameter reflecting telescope will provide astronomers with access to the visible, infrared, and submillimeter spectrum, with optimized performance in the mid-infrared to submillimeter range (see Figure 5.3). By recording infrared measurements not possible from the ground, SOFIA will help answer many fundamental questions about the creation and evolution of the universe, including how stars and planets are formed, how organic materials necessary for life form and evolve, the nature FIGURE 5.2 The first-generation SOFIA instruments. SOURCE: Stratospheric Observatory for Infrared Astronomy, The Sci- ence Vision for the Stratospheric Observatory for Infrared Astronomy, NASA Ames Research Center, available at http://www. sofia.usra.edu/Science/docs/SofiaScienceVision051809-1.pdf.

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 THE STRATOSPHERIC OBSERVATORY FOR INFRARED ASTRONOMY TABLE 5.1 SOFIA’s First-Generation Instruments Instrument Description HAWC High-resolution Airborne Wideband Camera EXES Echelon-Cross-Echelle Spectrograph FIFI LS Field Imaging Far-Infrared Line Spectrometer FORCAST Faint Object Infrared Camera for the SOFIA Telescope CASIMIR Caltech Submillimeter Interstellar Medium Investigations Receiver GREAT German Receiver for Astronomy at Terahertz Frequencies FLITECAM First Light Infrared Test Experiment Camera SAFIREa Submillimeter and Far-Infrared Experiment HIPO High-speed Imaging Photometer for Occultation GUIDERS Guider cameras WV MONITOR Water Vapor Monitor a SAFIRE has been deselected. SOURCE: Stratospheric Observatory for Infrared Astronomy, The Science Vision for the Stratospheric Observatory for Infrared Astronomy, NASA Ames Research Center, available at http://www.sofia.usra.edu/Science/docs/ SofiaScienceVision051809-1.pdf of the black hole at the center of our Milky Way Galaxy, and the size and composition of the outer bodies of the solar system. SOFIA will have a huge advantage over ground-based telescopes as it can fly anywhere on Earth (assuming overflight permission) to capture transient events that can be viewed only at certain times from certain locations, such as occultations of stars by solar system objects. SOFIA will also be able to observe at angles closer to the Sun than infrared space observatories, allowing studies of Venus and comets close to the Sun. FIGURE 5.3 SOFIA’s wavelength coverage and design lifetime, compared with those of some other astronomical missions. The atmospheric transmission windows from a good ground-based observatory site are also indicated. SOURCE: Stratospheric Observatory for Infrared Astronomy, The Science Vision for the Stratospheric Observatory for Infrared Astronomy, NASA Ames Research Center, available at http://www.sofia.usra.edu/Science/docs/ SofiaScienceVision051809-1.pdf.

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 REVITALIZING NASA’S SUBORBITAL PROGRAM 5.4 SOFIA’S INSTRuMENTATION DEvELOPMENT PROGRAM The SOFIA instrumentation development program will include the development of new science instruments (both facility-class and principal-investigator-class), upgrades of existing PSIs, and studies of instruments and technology. The next call for instruments will be at the release of “First Science” in fiscal year (FY) 2011. There will be additional calls for new instrumentation development every 3 years, and the project anticipates one new instrument or upgrade per year. The approximate funding level for the new science instrument development pro - gram will be ~$10 million per year. 5.5 TRAINING OF uNDERGRADuATE AND GRADuATE STuDENTS The U.S. and German science communities have identified the continuous training of instrumentalists as a high priority. SOFIA will contribute to this objective by enabling the training of students and faculty in instrument hardware and software development. SOFIA will provide a valuable environment for students to participate in hands-on development of forefront technologies, an opportunity generally not available to students working on sat - ellite projects. SOFIA will inspire the next generation of young experimental astrophysicists to develop their talents in many areas of science and engineering as well as conducting and analyzing observations of SOFIA’s telescope. Just as with the Kuiper Airborne Observatory (KAO), SOFIA graduate and postdoctoral students will form a rich reservoir of talent that will become the next generation of principal investigators and instrument scientists. 5.6 EDuCATION AND OuTREACH As part of its overall mission, SOFIA has been designed to incorporate a strong educational and public out - reach program to help improve U.S. education in science, technology, engineering, and mathematics. SOFIA will serve as a major NASA research observatory where non-scientists and scientists can interact closely in a research environment. SOFIA has been designed to give elementary-, secondary-, and college-level educators from across the United States hands-on participation in cutting-edge scientific and astronomical research. There is consideration of running a National Science Foundation-funded REU program based on SOFIA. The major education effort, however, is to involve K-12 teachers, college professors, planetarium directors, and other educators in the science flights. This will give them direct, hands-on experience of cutting-edge research in a major observatory, as well as exposing them to the excitement of research in near space. The expectation is that ~75 educators per year will be able to fly on SOFIA, and each of them will bring back to his or her classroom both the knowledge gained and the excitement engendered. This multiplier effect (“a thousand teachers, a million minds,” to paraphrase Rising Above the Gathering Storm [NAS-NAE-IOM, 2007]), will indirectly benefit many hundreds of students a year. Adequately supported, SOFIA can be the world’s leading far-infrared and submillimeter observatory for much of the next 20 or more years. —Charles Townes, Nobel Laureate, Co-inventor of the laser, and Infrared Astronomer 5.7 FINDINGS AND RECOMMENDATIONS Schedule Finding: SOFIA has been a long-term development effort that will provide a platform for future IR instrumen - tation development with potential for major scientific discovery as the platform will allow routine access to IR frequencies not accessible from the ground or from other spacecraft. The science community has been waiting since 2001 for the new facility.

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 THE STRATOSPHERIC OBSERVATORY FOR INFRARED ASTRONOMY Recommendation: An operational SOFIA should be brought to completion as safely and expeditiously as possible. Instrument Development Finding: The first-generation instrument suite planned for the early flights of SOFIA represents state-of-the art astronomy instrumentation for today’s science questions. The next call for instruments will be at “First Science” in FY 2011. Recommendation: It is critical that NASA hold to the Fy 2011 call for proposals and create an on-going instrumentation development program to ensure that SOFIA will be operating at the cutting edge of tech - nology during its entire flight lifetime. Workforce Finding: There is concern that there may be insufficient workforce to handle the full-up utilization of SOFIA together with the simultaneous operation of other ASP aircraft missions. Recommendation: Sufficient long-term budget and workforce planning will be needed to achieve the full science return possible from the full suite of world-class facilities that the NASA aircraft represent.