A NASA Jet Propulsion Laboratory manager Tuesday said a General Accounting Office report released last week was erroneous in its conclusion that JPL planetary mission data were lost in storage.
The GAO report implied considerable damage had been done to JPL's data tapes from past planetary missions while the tapes were stored at the Federal Records Center in Laguna Niguel.
"Virtually no data from past JPL planetary missions has been lost," said Arthur Zygielbaum, manager of JPL's Science Information Systems Office. In fact, JPL has active programs to make this data easily accessible and useful to scientists for generations to come, he said.
For example, JPL is currently storing and distributing data on compact disks -- read-only memory (CD-ROMs), which are like compact disks in home stereos. Each disk can hold data equal to more than five full magnetic tapes.
Data from the 135,000 tapes recently recalled from the federal facility are being cataloged.
The GAO had said 50 percent of the tapes may be damaged beyond recovery or contain data of little or no value.
"In contrast," said Zygielbaum, "of the 35,000 evaluated so far 90 percent were valuable and useful and 10 percent were duplicated data or backup material. "The GAO report said that NASA has not performed an agency wide inventory on data holdings," he said. "It is more accurate to say that NASA has not completed such an inventory. NASA has initiated a data census effort involving JPL and the Goddard Space Flight Center in Maryland and is developing a Phase One report on this effort.
"The GAO complained that JPL was spending scarce resources to store data of little or no value. In fact JPL is in the process of evaluating the 135,000 tapes to determine what is disposable. Prior to the evaluation no one can say what percentage of that data is of no value."
The GAO report was quoted as asserting that the 1983 Planetary Image Conversion Task efforts to restore 10-year old tapes often led to their destruction.
Zygielbaum stated that the task, which cost $459,000 in 1983, resulted in preserving 99 percent of the data in question and converting that data to higher density media (and fewer) tapes. "In the end some of the old tapes were indeed destroyed," he said, "but only after the data was successfully copied."
In 1988 JPL recognized the need to initiate a follow-on effort and the Planetary Data Restoration Project was started with four main goals.
They were to preserve data and make data available to the user; to move all magnetic tapes to an acceptable environment immediately; to reduce the volume of magnetic tapes by converting to higher density media and disposing of duplicate and/or worthless tapes; and finally to transfer converted tapes and archive responsibility to the Planetary Data System (PDS) or other appropriate NASA facility.
According to Tom Renfrow, Manager of the PDS, "Of the 140 gigabytes (giga=billion) the PDS is responsible for, over 20 gigabytes have been cataloged and are being prepared for distribution on CD-ROMs."
While JPL officials expressed concern that some of the GAO's comments were incorrect interpretations of fact, they agreed that NASA's space data represents an important national resource and thus they are taking steps to maintain it.
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