HUT is currently scheduled to fly on Endeavour on February 23, 1995.

Astro-2 continues the exploration of the invisible universe of ultraviolet astronomy, building on the experience and scientific data obtained on the first Astro Flight. This Second mission will fill gaps in our knowledge about ultraviolet astronomy, expand and refine existing data, and help astronomers better understand our dynamic universe.

The Observatory

The Astro observatory consists of the Hopkins Ultraviolet Telescope, the Ultraviolet Imaging Telecope, and the Wisconsin Ultraviolet Photo-Polarimeter Experiment. These instruments have been carefully maintained and , in one case, upgraded since the first mission.

Spacelab components hold and point the instruments and allow the crew and scientists to conrol operations during the mission. Spacelab is a system of pressurized modules, open pallets, and specialized support structures designed to provide a flexible system for performing scientific investigations on the Space Shuttle. Built by the European Space Agency as part of an international partnership with NASA, the different components can be "mixed and matched" to meet the needs of any set of investigations.

For Astro missions, the telescopes are attached to the Spacelab Instrument Pointing System (IPS) using a structure called the cruciform. The telescopes are co-aligned on the cruciform to make possible simultaneous observations of the same target. Mounted on two Spacelab pallets carried in the Space Shuttle payload bay, the IPS moves in three axes (roll, pitch, and yaw) to provide aiming with 1-arc-second angle of accuracy even as the Shuttle moves. (If you put a pinhole in a pinhole in a sheet of paper and hold that paper at arm's length, the sky you can see through the pinhole is approximately 1 arc-second in width.) An image motion compensation system will improve stability during observations. Equipment to provide power, telemetry, and commands to the instruments is in a pressurized container, called the igloo, located at the head of the two pallets.

The Mission

Scheduled for launch in late 1994, Astro2 will continue the work begun on the first mission. During the planned 16-day flight, operations will continue around the clock so as many observations as possible can be made. Generally, fainter targets will be observed during the "night" portion of the orbit, when Earth is between the Shuttle and the Sun, and brighter targets will be observed during the day.

Planning for the mission began in 1991 when the second mission was approved. NASA management and the instrument teams then began working together to ensure that the equipment was ready for flight and to develop a mission timeline, a detailed "blueprint" of all activities to take place during the mission. The scientists on the ground and the crew in orbit will use this timeline to conduct scheduled observations.

Astronomers will receive telescope data at Spacelab Mission Operations Control and adjust their observations as needed to obtain the best possible results. If the data reveal something unexpected or if an unforeseen astronomical event occurs -- as happened during Astro-1 with the outburst of a cataclysmic variable star -- the instrument teams will work with the cadre to develop changes to the timeline. This allows the investigators to explore the unexpected and take advantage of science opportunities that may arise during the mission.

This text was taken from the NASA produced pamphlet ASTRO-2 Continuing Exploration of the Invisible Universe produced in September 1994.

Mary Romelfanger (