Poised on Pad A, Complex 39 at the Kennedy Space Center, the space shuttle Challenger has had its windows cleaned and loose debris removed. It's ready to carry a crew of five into orbit Saturday.
If all goes well, the launch, now scheduled for 7:33 a.m. Eastern daylight time, will make history. A crew member, Sally K. Ride, will become the first woman astronaut from the United States to enter space.
But apart from that positive precedent, not even 100 percent success for this seventh shuttle mission would dispel the clouds that obscure the future of the US Space Transportation System.
STS, as the National Aeronautics and Space Administration (NASA) calls it, is much more than the shuttle. It's a complex, interdependent network of flight control, ground maintenance, and launch facilities, and the industrial capacity that backs it all up. Last April, the National Research Council - an agency of the National Academy of Sciences - told Congress that, taken as a whole, there is no way this system can meet NASA's goal of 24 launches a year by 1988, 30 per year by 1990, and 40 per year by 1992.
The research panel estimated that 18 shuttle launches a year would be a more realistic expectation for the presently authorized fleet of four orbiters. Even so, a lack of spare parts, including the solid rocket boosters needed for launching, would make the possibility of meeting such a launch schedule ''marginal.''
NASA would like to have a fifth orbiter. But both the Reagan administration and Congress have been reluctant to make such a commitment. Meanwhile, there continues to be concern both within the administration and Congress and within NASA over the commercial future for the STS as a launcher of communications and other satellites. The European Ariane rocket - one of which was scheduled for launch today carrying two communications satellites - is a strong competitor for that business. Also, the administration is eager to sell NASA's old rockets to private companies, which then would compete with the shuttle.
Were the shuttle unable to secure a profitable share of the launch business, the STS, developed at a cost of $15 billion, would have a greatly diminished role in US space activity. It would be used mainly for military purposes, such as launching spy satellites, and for NASA projects.
Such is the uncertainty that overshadows the six-day STS-7 mission. Yet it should demonstrate many of the capabilities that NASA hopes will make the shuttle a winner.
To begin with, there will be two commercial satellite launches - the communications satellites Anic C of Canada and Palapa B of Indonesia. Then astronauts will use the West German-built space platform SPAS (Shuttle Pallet Satellite) to demonstrate Challenger's ability to rendezvous with and retrieve a free-orbiting satellite.
The crew will use the movable arm supplied by Canada to manipulate and deploy SPAS and later to retrieve it. This exercise will help lay the foundation for a satellite rescue during the STS-13 mission. Then it is planned that astronauts will retrieve the malfunctioning Solar Maximum Mission satellite - a sun-observing satellite - and repair it in the payload bay.
One of the most important STS-7 objectives is to show that the shuttle can return to the Kennedy Space Center, its main base for civilian operations. As now planned, shuttle commander Robert L. Crippen is to bring Challenger down on Runway 15, a 3.2 mile north-south strip.
Such a busy mission requires a substantial crew. Besides mission commander Crippen and shuttle pilot Frederick H. Hauck, mission specialists John M. Fabian and Dr. Ride are needed to meet all objectives.
Meanwhile, Dr. Norman E. Thagard - a fifth astronaut who was not part of the original crew - will be studying his colleagues. He is to carry out medical tests and collect physiological data to learn more about how humans adapt to space flight.
NASA officials are proud of the speed with which Challenger has been refurbished for this mission. A June 18 launch would be 60 working days (64 calendar days) from the start of the work - the fastest processing so far. But, as the research council report emphasized, it will take a great deal more than skill in orbit and snappy procedures on the ground to make the STS a success. A long-term program to guarantee adequate spare parts and other logistical necessities is urgently needed. This is something that NASA has only begun to put together.