Backlog Could Delay Space Probe : Venus Mission Fights for ‘Seat’ on Shuttle

A small space probe that should help scientists understand why Venus, the planet that should be most like Earth, evolved instead into a lifeless hellhole will be delayed for at least two years unless it edges out a couple of giant competitors when the space shuttle finally resumes its flights.

A six-month slip in the schedule is expected to delay the first shuttle flight until at least the fall of next year, which would put it perilously close to the scheduled launch of the Magellan Venus Radar Mapper. And because of the backlog of projects waiting to be launched from the shuttle, Magellan will have to beat the Defense Department and the Hubble Space Telescope to meet its desired launch date.

Timing is everything for the spacecraft because if it does not begin its long journey in April, 1989, Venus will not be in the right position again for Magellan to be launched until May, 1991.

10 Years Since Last Probe

If it makes the 1989 date, the $250-million spacecraft will be NASA’s first planetary probe since Voyagers 1 and 2 took off for their grand tour of the outer planets 10 years ago. Magellan, a Jet Propulsion Laboratory project, was built partly out of spare parts left over from previous planetary programs, and by the time its mission ends it should have provided scientists with continuous, three-dimensional profiles of the surface of Venus.

“We were No. 8 on the schedule with a February launch date” for resuming shuttle flights, said Magellan Project Director John Gerpheide, “but the shuttle is not going to start flying again in February.”

A decision by NASA to test-fire the shuttle’s main engines before resuming flights has pushed the first launch back.

“We have to start inching up in the launch sequence, maybe to No. 4” if the April date is to be met, Gerpheide said.

To do that, some of the projects already scheduled for launch ahead of Magellan would have to be delayed slightly, a suggestion that is not especially popular among scientists who are as eager as Gerpheide to see their own missions launched.

Gerpheide and other scientists at JPL in the hills above Pasadena argue that a one-month slippage for other projects would not be as damaging as a two-year delay for Magellan. JPL has been through that demoralizing process several times in recent years, and scientists there say the most difficult challenge during such a period is to hang on to the project’s key scientists and engineers while there is little work for them to do.

“We would worry about keeping the team together,” Gerpheide said. “The team is No. 1.”

Struggle for Priority

The new crunch has led to bureaucratic struggling within the space agency as various divisions fight for priority for their missions.

“It’s scary,” Gerpheide said. Scheduling “is a big problem to everybody. You end up arguing over the sensible sequence of missions.”

“There doesn’t appear to have been any blood drawn yet,” said NASA headquarters spokesman Charles Redmond, who noted that NASA at this point is not sure what the final schedule will look like or even when the flights will resume.

“We are in a totally flexible mode,” Redmond said.

Sympathy for JPL’s predicament runs high at NASA headquarters, according to Redmond and Gerpheide.

“Everybody wants to get the planetary program started again,” Gerpheide said.

But that does not mean it will be easy.

At least two of the early missions cannot be delayed, according to NASA. The first shuttle flight is to carry a tracking and data relay satellite that is crucial to subsequent missions. Only one such satellite is operating, and NASA needs two in order to provide total coverage. Furthermore, the one that is in operation is several years old and has experienced intermittent outages. If that should fail, a second satellite would have to be launched before other projects could be considered.

“And there’s at least one DOD (Department of Defense) mission that will outrank us,” Gerpheide said.

At best, that would place Magellan third or fourth in the pecking order.

And that would mean the launch of the Space Telescope, which NASA has described as the most important scientific instrument it has ever built, would have to slide at least a month. So would an astrophysics laboratory from the Goddard Space Flight Center, which was supposed to have made its first flight in time to observe Halley’s comet last year.

Hanging On to Seat

Although a short delay for space projects such as those might not seem catastrophic, no one is eager to give up an assigned seat.

That is apparent even in the Magellan schedule. If it is launched in April, 1989, it will have to travel for 16 months to get to Venus, a trip that will take it around the sun once while it waits for the planet to reach the right spot in its orbit. Normally, a trip to Venus would only take about five months, but the best launch dates for the shorter routes are already taken--one in late 1989 by JPL’s Galileo spacecraft, which is already several years behind in its journey to Jupiter, and one by the European spacecraft Ulysses, which will be launched in 1990 to study the polar regions of the sun.

Thus Magellan will be in a holding pattern for most of its journey to Venus, but that beats sitting on the ground waiting for a better launch date, Gerpheide said.

“You take what you can get,” he said.

Since planetary probes can only be launched when the planets are in the right position, there are few opportunities for launches, and similar circumstances sometimes dictate the launch times for other probes, such as some surveillance satellites. If it turns out that the Defense Department needs the same time slot as Magellan, “that’s when you’ll see blood on the walls” at NASA headquarters, Redmond said.

He added that the Defense Department also seems willing to negotiate whenever possible in view of the competing demands for the shuttle, which has been grounded since the Challenger blew up in January, 1986.

Best Look Yet

When it finally arrives at Venus, in August of 1990, if JPL has its way, Magellan will give scientists their best look yet at the nearby planet.

“We will map approximately 90% of the planet,” said Steve Saunders, the project scientist.

Magellan will go into a near polar orbit about Venus, which rotates on its axis once every 243 days. The spacecraft will orbit Venus every 3.1 hours, and the planet will have rotated slightly within the orbit with each passage. Thus, the high resolution radar mapper on the spacecraft will cover nearly the entire surface in 243 days.

“We will produce as much image data as NASA has produced to date,” Saunders said. “Greater than the combined total of all previous missions.”

In the past, planetary missions literally filled warehouses with magnetic computer tapes containing data from the probes.

But Magellan will use the new technology of compact disks, which look exactly like the audio disks popular with audiophiles. These disks, however, will serve as memory banks for personal computers, and one disk can hold the equivalent of a roomful of magnetic tapes, Saunders said.

That means every scientist can have a complete record of the Magellan mission, with total access through an ordinary personal computer.

The images from the mission “will look pretty much like aerial photos,” and they should be sharp enough to allow scientists “to work out the geological history of Venus in great detail,” Saunders added.

That history is of special interest to scientists because Venus is so similar to Earth in so many ways--in density, mass, size and distance from the sun, for example--that it should be very much like the Earth, Gerpheide said.

“But it isn’t,” he added. “It’s a lot different.”

With surface temperatures ranging up to 700 degrees Fahrenheit above zero and crushing atmospheric pressures 90 times greater than Earth’s, Venus is devoid of life. The planet that should be the most like Earth is a barren, inhospitable rock.

‘Had Water at One Time’

“Surely it had water at one time,” Gerpheide said, although previous planetary probes found no sign of it.

Could it be that Venus is a victim of the “greenhouse effect,” the gradual buildup of carbon dioxide that trapped heat in the lower atmosphere, dissipating water molecules? Some scientists fear that may be happening now to Earth.

If microorganisms had formed on Venus during the early stages of its history, consuming carbon dioxide and emitting oxygen, would the planet look much more like Earth today?

Possibly, Gerpheide said.

“All we know is it evolved in a dramatically different way,” he said.

A better understanding of that process could have significant implications for Earth, the only planet in the solar system capable of supporting life, he added.