- About PSI
1. What is the Atsa advantage?
This is a very low cost space telescope. Because of our low cost (and because we can easily replace parts), we can take many risks that other space telescopes cannot. Chief among these is our ability to observe targets close to the Sun. This opens up a class of targets currently inaccessible to space telescopes: not only Venus and Mercury, but also families of near-Earth Asteroids, sun-grazing comets, and even Vulcanoid searches. Observatories such as Hubble and the Spitzer Space Telescope cannot look too close to the Sun for fear of endangering instruments in the focal plane.
The high responsivity of the Lynx platform and short time required for integration will make Atsa a valuable asset in responding to astronomical transients, such as supernovae or optical transients of gamma ray bursts. Depending on where in the sky a transient occurs, Atsa can be integrated, launched and pointed at a target in less time (and at lower cost) than it would take to plan and retarget the Hubble Space Telescope or other similar space-based assets.
2. Why the XCOR Lynx?
For the last 50 years, the main workhorse vehicle for suborbital sounding rockets has been the Black Brant family of launch vehicles. These give a payload 10-20 minutes of microgravity (which is also time above the atmosphere). Each Black Brant flight costs approximately $1-2 million. The payload is subjected to high g-loading on launch and re-entry, and splashes down into the Atlantic Ocean at the end of the flight. Any payload re-use requires a rebuild of the instrument. The maximum payload diameter is 17.26 inches, which limits the size of telescope that can be carried.
The reusability of the XCOR Lynx, by contrast, significantly reduces per-flight cost and accommodates the larger aperture of the Atsa Suborbital Observatory. Upon the completion of a flight, Atsa will be ready for quick turnaround and reuse, without rebuilding.
3. Team Members
The Atsa Project is a collaboration between two institutions: the Planetary Science Institute and the Citadel, the Military College of South Carolina. Atsa began as a collaboration between Dr. Faith Vilas, at the time Director of the MMT Observatory (now a Senior Scientist at PSI), and Dr. Luke Sollitt, then at Northrop Grumman Aerospace Systems (now an Assistant Professor of Physics at the Citadel and an Associate Research Scientist at PSI). Drs. Vilas and Sollitt come from NASA science mission backgrounds. Dr. Vilas is an expert on using space-based telescopes to study debris, having designed experiments for observing human-made debris with the DOD MSX satellite. She is also a Participating Scientist for NASA’s MESSENGER mission to Mercury, and a U.S. Science Team member for JAXA’s Hayabusa mission to Asteroid 25143 Itokawa. Dr. Sollitt’s work in graduate school was with the Advance Composition Explorer spacecraft; he went on to be a co-inventor of and co-Investigator with the LCROSS mission to the Moon that discovered a water ice deposit in a permanently shadowed crater at the lunar South Pole. They have brought a space systems engineering approach to Atsa development, despite the extremely low cost of the system.
4. Atsa One Camera Description
The Atsa One Camera is an engineering testbed for the eventual Atsa Suborbital Observatory. It consists of a (TBR) five-inch-diameter modified Cassegrain telescope, connected to a five-position filter wheel and a Xybion ISS-750 visible-NIR camera. The components are assembled on a truss, which is mounted to a Cartoni fluid-head TV camera mount. The entire assembly is mounted onto the XCOR Lynx’s armrest with a team-designed mounting bracket. A guide camera with a larger field of view is mounted next to the primary fore-optic. Data acquisition is done with a Dell E6400XFR ruggedized laptop computer which is mounted behind the pilot’s seat in the “Payload A” box. Power is provided from a perfect sine wave converter that takes DC volts either from the spacecraft or a battery. The adapter, the battery, and the camera control box (which controls intensity, offset, and so on) are all mounted in the Payload A box along with the computer. User controls for data acquisition and filter wheel control are in a team-designed control box attached to the mounting bracket. The instrument launches powered-on and ready to commence data collection; the spacecraft trajectory is planned out prior to each launch to minimize maneuvering; and the instrument itself is steered by the observer to achieve the sub-degree pointing needed to accommodate the narrow field-of-view reproduced in simulation of the eventual larger Observatory.
Safety is first in instrument design. A great deal of margin for g-loading is included . There are no deployments apart from the unlocking and re-locking of the fluid head mount locks. Even if the mount is not locked prior to entry, the loads on the mount will not exceed what a typical television cameraman on Earth would feel with a large camera. During fit testing of the Atsa One Camera in August 2012, XCOR Aerospace’s chief safety officer inspected the set-up and pronounced the system “uninteresting from a safety point of view”, which is to say, safe.
6. Test flight sequence
The Atsa team has identified a series of eleven flights to fully prove out the concept of human-tended suborbital astronomy and the Atsa control paradigm. The objectives for each flight are separated into three categories: science floor, science baseline, and optimal. If a flight accomplishes its science floor objectives, it is deemed a success, and we move on to the next flight in the series. We use observations of Venus and Mercury to test our capabilities; in later flights, we conduct observations successively closer to the Sun (a reduced solar exclusion angle is one of the paramount capabilities a system like Atsa offers over space telescopes such as Hubble and Spitzer).
The structure for our flight sequence was inspired by the Apollo paradigm. During Apollo, each new flight was an envelope expansion over previous flights. Apollo 7 was the first CM flight. Apollo 8 extended the CM test to lunar orbit. Apollo 9 tested the LM; Apollo 10 took the LM to lunar orbit. Apollo 11 then extended the LM down to landing. We will follow a similar philosophy, where each new flight builds on the lessons of previous flights and tests new, expanded capabilities (and provides additional demonstrations of previously-tested capabilities). Our flight sequence is deliberately conservative. It is conceivable that the overall science floor can be met in two flights, and achieve a full proving of the system with six flights or fewer.