Once again, the space shuttle Discovery is ready for a mission with several orbital ``firsts.'' Its crew includes Prince Sultan Salman Abdel Aziz al-Saud, a jet-rated pilot and acting director of the Saudi Arabian Television Commercial Department, and French astronaut Patrick Baudry. This is the first shuttle mission to carry two foreign crew members and the first Saudi astronaut to enter space.
Spartan 1 -- a free-flying astronomical observatory to be deployed and then recovered by Discovery -- is to inaugurate a new capability for relatively inexpensve yet powerful space research.
The Strategic Defense Initiative (SDI) program is flying a laser reflector to test the precision of ground-based lasers in tracking low-orbit objects. This is the first of a number of ``star wars'' experiments to be flown on shuttle flights.
Mission 51-G was on schedule for launch from Florida's Kennedy Space Center at 7:33 a.m. EDT today, as of this writing. Discovery is to return to Edwards Air Force Base, Calif., seven days, one hour, and 41 minutes later, according to the National Aeronautics and Space Administration (NASA) flight plan.
NASA officials have decided to bring this mission and several future flights into Edwards until they solve the problem of brake and tire damage apparently associated with the rough runway surface and restricted maneuvering space at Kennedy. Shuttles landing there have experienced serious brake damage and scuffed or blown tires. Yet Challenger, with Spacelab on board, had no such problem when it landed at Edwards on May 6.
Discovery is carrying three communications satellites to be launched for commercial customers -- the AT&T Telstar-3D, Mexico's Morelos-A, and Saudi Arabia's Arabsat-1B. These launches will be managed by regular NASA mission specialists Shannon W. Lucid, John M. Fabian, and Steven R. Nagel, while mission commander Daniel C. Brandenstein and shuttle pilot John O. Creighton will handle the spacecraft.
But, while Prince Sultan will only watch the Arabsat launch, NASA's policy of allowing a customer to send along a mission specialist has given him a doorway to space. His assignment includes photography of Saudi Arabia during the 49 daylight passes of Discovery. Geologists at the University of Petroleum and Minerals in Dhahran plan to compare the pictures with earlier data taken by radar and by orbiting mappers and scanners. They also hope to study geological features such as sand-dune formations.
Prince Sultan also will help astronaut Baudry with physiological research. Baudry is on board to manage a French echocardiograph experiment and to make other medical tests. His instrument tracks blood flow by means of ultrasonic waves. The instrument provides images of the heart and abdominal organs and of blood flow through blood vessels. It records movements of cardiac walls and valves.
For many space scientists, however, Spartan 1 is likely to be the center of interest. This is the first of a series of self-contained instrument platforms that extend the shuttle's scientific capacity. Such platforms are dropped off early in a shuttle mission, then retrieved and returned to Earth at the mission's end. They are controlled by on-board computer programs, and they record their data on tape for later analysis on Earth.
Spartan 1 carries an X-ray sensor to study X-ray sources in deep space and in the center of our own galaxy. Recently reported studies by Charles Townes and colleagues at the University of California have reinforced the suspicion of some astronomers that the galactic center contains a massive black hole. This would be an object so massive and compact that its gravity would be too strong for even light to escape it. Spartan data may give more insight into the nature of this phenomenon.
But the most important aspect of its mission is simply to show that Spartan equipment can do its job well. Such robot satellites offer scientists a means of space research that is intermediate between the rare opportunity to fly expensive, often elaborate Spacelab instrumentation and the more available, very low-cost, and generally simple, ``Getaway-Special'' cannisters carried in the shuttle bay.
If they prove to be practical, Spartan platforms may relieve some of the frustration that university space scientists, especially, have felt over the limited research opportunities the shuttle system has afforded them so far.