The secrecy surrounding January's space shuttle flight and its military payload marks a turning point for the United States manned spaceflight program. From Mercury 3 in 1961 to last month's shuttle satellite-rescue mission, all 46 manned flights have been open and essentially civilian in nature. Many astronauts have been, and still are, military officers. But they have been seconded to the civilian space agency to carry out civilian duties. Now they will do the Defense Department's (DOD) work on some missions - missions that defense officials say must involve large measures of secrecy to protect national security.
That is why defense officials were so startled Dec. 19 when the Washington Post, and subsequently other media, reported that the crew of Mission 51-C would launch a spy satellite and in very general terms described its capabilities.
Other news organizations, including the Associated Press, NBC News, and Aviation Week & Space Technology, had similar information. But they suppressed it at the request of defense officials, who argued that national security would be compromised if it were published.
Defense Secretary Caspar W. Weinberger characterized the Post report as ''the height of journalistic irresponsibility.'' Post executive editor Ben Bradlee replied that ''there is nothing in the article that violates national security, and the public is ill-served by silence.''
The virtual news blackout on Jaunary's flight may disappoint a public accustomed to daily accounts of astronaut adventures. But STS managers at the National Aeronautics and Space Administration (NASA) would like to have many more DOD missions. This is not because they have any passion for secrecy. It is because they know the shuttle system won't be economically viable without expected DOD business. And mission secrecy is part of the deal.
The Defense Department has fostered a new breed of military astronaut. Air Force Maj. Gary Payton, who will manage the Mission 51-C payload, is one of 25 members of the DOD's Manned Space Flight Engineer Corps. They have been recruited and trained specifically to handle military payloads by taking part in their development. Major Payton will work with four NASA astronauts - Navy Capt. Thomas Mattingly, mission commander; Air Force Lt. Col. Loren Shriver, shuttle pilot; and two mission specialists, Air Force Maj. Ellison Onizuka and Marine Lt. Col. James Buchli.
What military work has been done on past manned flights has been minor, as in the case of the Air Force experiment carried along on the fourth shuttle mission in 1982. On that occasion and for that experiment only, astronauts had secure communication with an Air Force control center in California instead of with the Mission Control Center in Houston.
But 20 percent of the 70 or so shuttle flights envisioned between now and 1990 are expected to be paid for by the Department of Defense. Many will be launched from a shuttle facility under construction at Vandenberg Air Force Base in California. These missions are also expected to be carried out under the general secrecy rules announced officially at a Washington briefing last Tuesday. Worked out between Pentagon and NASA over many months, and already reported by the press, they contain nothing unexpected. The rules are to apply uniformly to all military shuttle missions even though the payloads will vary in sensitivity. This is to avoid highlighting truly sensitive missions by imposing unusually tight restrictions on those occasions.
Briefly stated, there are to be no news conferences with mission crews, no press kits, no information on cargo, no public access to astronaut communications on orbit. Launch times will be announced in advance only within a three-hour ''window.'' This is to deny Soviet trackers the information needed to preset their equipment. Landing times will not be announced until 16 hours before touchdown. There will be no mission commentary until then. But there will be brief status reports every eight hours.
Limited countdown status reports will also be given, starting an hour before the three-hour launch window opens. There will be limited broadcast of astronaut communications during the shuttle's ascent and again, perhaps, during reentry.
If there were an emergency on orbit, the news flow would open up, except for maintenance of payload secrecy. Any shuttle malfunction would be openly reported , as would astronaut efforts to return safely.
Nevertheless, secrecy in such matters is a slippery concept. Even before the Post story, it had already been reported that the 51-C satellite is to be placed in the 22,300-mile-high geosynchronous orbit. In relating this Nov. 5, Aviation Week noted that DOD spacecraft sent to this orbit in the past have included communications satellites, missile early-warning satellites, and electronic surveillance satellites equipped to intercept radio transmissions. The report added that ''these basic types of military missions launched from the Cape (Canaveral) have not changed with the advent of the space shuttle.''
The DOD information officer, Brig. Gen. Richard Abel, raised eyebrows by suggesting that any press ''speculation'' as to the nature of a shuttle's military payload could trigger a DOD investigation to see if national-security laws had been violated. His deputy, Col. Michael P. McRaney, later softened this comment by explaining thatpress reports would not automatically spark an investigation. That would ensue only if it seemed likely that a genuine leak had occurred, he said. But he did add that speculation about payloads would be viewed with concern.
After release by the shuttle, the satellite will be boosted to this higher orbit by the Air Force Inertial Upper Stage (IUS) booster rocket.
This booster's embarrassing public failure put a $100 million Tracking and Data Relay Satellite (TDRS-A) into the wrong orbit during the sixth shuttle mission April 5, 1983.
The Air Force and NASA believe that the booster can be trusted again. Thus, if it works with the secret DOD satellite, they will want the world to know about it. They are expected to break their own secrecy rule and report the IUS performance.
Mission 51-C is now scheduled for launch from Cape Canaveral sometime between 1:15 p.m. and 4:15 p.m. Eastern standard time on Jan. 23.