SOFIA's high cruising altitude will enable astronomical observations above 75 percent of the atmosphere, above nearly all of the water vapor column, and with a cloud-less low-extinction view on the horizon. This provides low scintillation for occultation studies, low absorption in the water vapor bands for near-IR, mid-IR, and submm observations, and 4 - 5 times higher meteor rates than are seen from the ground. Observations from the Upper Deck on SOFIA could help answer key science questions and issues as defined in the NASA Space Science roadmaps.
Space Science Fundamental Questions:
- How does life begin and evolve?
- Where do we come from? Where are we going?
- How does the Earth respond to solar interactions with the Earth's atmosphere and space environment.
- What are the impacts for humanity from space weather, changes of Earth's atmosphere, habitability of space.
Potential contributions of measurements based on the SOFIA Upper Deck:
- Determine any chemical precursors of life
- Characterize the cosmic and endogenous sources of matter (organic and inorganic) for potentially habitable environments
- Learn how the Sun's family of planets and minor bodies originated
- Understand how the solar system evolved to its current diverse state
- Determine the characteristics of the solar system that led to the origin of life
- Understand how life began and evolved
- Explore the space environment to discover hazards to Earth
- The chemical evolution of exogenous delivered organics
- Support of regular SOFIA observatory program for relatively bright objects such as comets and gamma-ray bursts
- The compositional diversity of comets and asteroids
- The search for extrasolar planets
- The long-term collection of stratospheric dust
- Satellite impact hazard mitigation
Search for extrasolar planets: How frequent are planets? How large are known asteroids? The lower scintillation onboard SOFIA makes it possible to perform occultation measurements at much higher precision than from the ground. For this reason the SOFIA High-speed Imaging Photometer for Occultations (HIPO) has been developed for use on the main telescope. Graph shows observations from the ground and space of the decrease in star brightness from an eclipsing extrasolar planet around V = 7.65 magnitude star HD209428. Upper Deck research would be uniquely suited for long-term surveys and for relatively bright background stars. Not inhibited by clouds, observations may include asteroid, Kuiper Belt comet, or Oort Cloud comet occultations of distant stars, and perhaps even gravity lenzing by brown dwarfs.
Diversity of minor bodies: How do comets and asteroids differ in elemental and mineral composition? Graph shows the rate of visible meteors per square degree from the ground and from altitude. Most appear near the horizon. The effect is stronger for brighter fireballs. This enables the systematic study of meteoroid composition. Ground: 1 spectrum per Perseid shower, 21 nights of sporadic observations for one spectrum. SOFIA: over 4 spectra per shower, less than 4 sporadic nights per spectrum. SOFIA also makes it possible to observe with Moonlight and in cloudy weather. Graph is from P. Gural and P. Jenniskens, EMP 82-83 (2000). Video shows a Taurid fireball, a fragment of comet 2P/Encke, observed over Nevada during the 2001 Leonid MAC mission from an altitude of 39,000 ft (M. Koop, P. Jenniskens).
Interactive interplanetary dust collection: SOFIA will fly high enough to facilitate the collection of interplanetary dust particles and aerosols. What is responsible for the frequent week to week changes in collected interplanetary dust properties? The interactive capability makes it possible to frequently exchange the collection container for high temporal (and spatial) resolution of dust grain collection. Image shows Melissa Pfeffer with the University of New Mexico Albuquerque dust collector onboard the USAF/NKC-135 FISTA aircraft curing the 2002 Leonid MAC mission.
Wide field imaging support of SOFIA main facility: The upper deck could also facilitate wide field optical observations of comets during SOFIA mid-IR and submm observations. Mid-IR observations of the sky background can support the telescope operations by alerting the presence of clouds (imaging) and variations in carbon-dioxide absorption (spectra).
Other science objectives may well be achieved, the topic of discussion at the first SOFIA Upper Deck Science Opportunities Workshop (June 22-23, 2004).