WHILE the Hubble Space Telescope team looks forward to the delayed launch of their observatory April 24 or 25, many members also have their eyes on the 21st century. ``In 20 years, 15 years, [or sooner], I'll be gone, for sure, and [so will] others,'' says Hubble project manager James Moore. He notes that, if the instrument is to maintain its scientific edge throughout that long period, the present team members have to prepare for future generations.
The team is concerned about the gradual degradation of telescope hardware. They plan to build new, more powerful instruments to put on board. They anticipate the need to continue training personnel and astronaut crews who will tend the observatory. At the same time, they know that they may not be around to help and advise.
``So, the people that are on the job now are leaving a legacy to make sure the follow-on folks have something to look at, study, and operate,'' Dr. Moore says.
The Hubble Telescope's near-perfect 94.5-inch mirror and a battery of sensitive instruments are expected to help astronomers answer questions about the birth and fate of the universe. It is the first scientific Earth satellite designed to be maintained and upgraded by astronauts for a 15- to 20-year expected useful life. But it is only the first. Other long-lived ``Great Observatories'' are to follow. The second of these - the Gamma Ray Observatory - is due on orbit in the fall.
This gives initial team members an obligation to posterity that adds a new dimension to a scientific satellite project. Starting years before launch, they must think carefully how to explain what they have done to their successors when their media for explanation are documentation, simulations, and test hardware.
Moore notes, for example, that astronauts and technicians now practicing the replacement of Hubble instruments are recording in detail all the steps involved. They want to show future maintenance crews exactly what they have done and why, even though they may not meet these future crew members personally.
One of the most important elements in this heritage is under construction here at the National Aeronautics and Space Administration Goddard Spaceflight Center in Goddard, Md. It is the vehicle electrical systems facility. That is the formal name for a replica of the Hubble spacecraft's back end, where the instruments and other replaceable equipment reside.
It has the exact form and shape of the telescope. All of the spare Hubble electronic elements will be brought into that facility and mated up. Then, any new equipment for the actual telescopes, including whole new instruments, will be put into the facility to see if it fits. It will also be tested there to make sure it is compatible electronically with what is already on the spacecraft. This will be a way of showing future project members what the current designers have done by leaving a working replica that can be used, developed, and expanded.
The other major part of the legacy is computer software and its detailed documentation. Software that runs the on-board spacecraft computer and the ground system will evolve throughout the life of the project. These changes will improve the telescope's capabilities as operators learn better how to manage it. Thus, Moore says, it is essential to leave clear records so future software designers will know exactly what was done in the past and why it was done.
Efficiency is a primary goal. Ideally, that means taking data on target 35 percent of the time. Moore does not expect to come near that goal at first. ``But, as the system matures and we understand better how to operate it, we hope to approach that,'' he says.
One of the best legacies current management could leave is a long-term plan to make the most of the Hubble facility under expected funding. As things stand now, Moore says he thinks that planning is in as good shape as it can be, given that fact that future funding can never be fully guaranteed.
``Probably the most expensive thing we're looking for in the future is the development of new instruments,'' he explains.
Currently three of these are under development, including a facility to allow Hubble to observe infrared wavelengths. Such instruments all are in the hundred-million-dollar class. ``If funding would not be sufficient to build those instruments, the telescope would degrade as the current instruments fail or degrade, and the telescope would become less useful,'' Moore says.
However, there is a long-term approved budget of $200 million a year and a long-term plan to make the most of it. Moore says that ``approved'' means funded through Congress' annual budget process. With that caveat, he says: ``I think we've got a well laid out program. If the telescope does reasonably well in orbit - which I have every expectation that it will - I see no [long-term] problem.''