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After almost 10 years, it's finally harvest time for the Galileo Science Data Team (SDT) (photo). There were years of waiting for launch and years of fleeting planetary and asteroid encounters. And finally there has begun what is to be a steady flow of data from Jupiter and its moons.
Unlike Voyager's flyby, Galileo will be orbiting Jupiter for years. Unlike probes around a single planet, Galileo is maneuvering amidst a planet and a swarm of varied moons.
The Galileo SDT, a member team of the Galileo Flight Control and Support Office, provides primarily downlink engineering support and services to the Galileo science instrument teams. These engineering support and service functions include development, system engineering, operations, and support of the central and clustered computer system known as the Science VAX Cluster (SVC); local and wide area network; Galileo Science Catalog (GSC); As-Run Spacecraft Events File (SEF); ancillary data (SPICE kernel) system; Multimission Image Processing System (MIPS); Multimission Photo Support Facility (MPSF); and temporary and permanent archive products design and planning and interface to the associated Planetary Data System (PDS).
SDT Team Chief Ted Clarke considers the Galileo Electronic Data and Communications Wide Area Network a key advance in how Galileo, and in fact all current and future space projects, conducts its business. In earlier missions, after data from spacecraft in deep space reached antennas of the Deep Space Network, they were preprocessed by computers at the DSN, relayed to computers at JPL and preprocessed some more. The data were then recorded on magnetic tapes, and the tapes put in padded mailing envelopes, driven to the local post office, and mailed to principal investigators around the world---often requiring weeks for transport and clearing customs before arriving at their destinations. This slow data flow from spacecraft to investigator was sped up by Clarke, working with then deputy manager of the Galileo Science and Mission Design Office, Clayne Yeates, and the NASA Science Internet office. Today, Galileo scientists anywhere in the world can log into the Galileo Science VAX Cluster, select the data set to be examined, and receive it in seconds. This speed is crucial in an orbital mission like that of Galileo if something unusual in the data might suggest changes in observation strategy for subsequent orbits. Galileo was at the cutting edge of electronic data communications and data transfer. Today the mainstream has caught up, and the Galileo network is part of the global Internet. The otherwise irrepressible Clarke, noting that Yeates died in 1991, mused "I wish he could see us now."
Another major contribution made by the Galileo SDT in the way space missions conduct their business was development of the Science VAX Cluster. The SVC, consisting of a central VAX computer and 10 VAX and SUN workstations, was developed by former SDT members Paul Fisher and Neal Cline and is currently evolved, managed, maintained, and administered by SDT members Bill Adler, Doug Clay, and Deborah Grayson. Besides serving as the central node of the Galileo network, the SVC provides computing capability for temporary storage and correlative data analysis for low-rate science experiments, and serves as the host for generation, storage, and operations of all ancillary data (SPICE) products, the GSC, and final versions of uplink sequence products, particularly the As-Run SEF.
The ancillary data system known as SPICE was developed by the Navigation and Ancillary Information Facility (NAIF). SPICE is an acronym that stands for spacecraft position (S), planet/satellite position (P), instrument alignment (I), camera/scan platform instrument and spacecraft pointing (C), and events (E). The Galileo implementation of SPICE was developed by Chuck Acton, Nat Bachman, Bill Tabor, Karen Deutsch, Paul Jepsen, Florance Moss, and Thuy Tran.
The GSC houses the SPICE kernels and uplink sequence products, and all quick-look and final low-rate science data files. The GSC was developed by former and current SDT members Irena Glazman, Qui Chau, Diane Conner, Thuy Tran, and Bill Adler. The GSC is now linked to the World Wide Web. This link was developed by Tran, Conner, and current member Dave Wasler.
Another first by the SDT is development of the As-Run SEF. This product electronically merges the baseline stored sequence with real-time commands subsequently uplinked to the spacecraft to allow for unanticipated, but subsequently required, spacecraft commanding. Prior missions kept paper records of the real-time commands. These paper products were often lost during subsequent years, and knowledge of the actual states of the spacecraft and instruments during important data gathering periods was seriously compromised. The As-Run SEF was developed by past SDT members Thuy Tran and Julie Wang and by current member Kuohwa Tan.
Orbital operations support by the SDT for SPICE and As-Run SEF operations is provided by Deborah Grayson, Pat Lynn, and Jean Maguire.
The MIPS and MPSF supports Galileo's high-rate science experiments---the solid state imaging camera, the near-infrared mapping spectrometer, and the plasma wave subsystem. This support includes processing the down-linked telemetry streams for making real-time, systematic, and science files, and generation of visible, infrared, and spectroscopic hard copy and transparency photo products for press conferences, maintaining the imaging library, and cataloging and archiving all high-rate science products. The Galileo operation of the MIPS and MPSF was led and managed by former SDT member Lisa Wainio, and currently by members Helen Mortensen, Jim Anderson, and Dave Deats, and their staffs of stellar engineers and operators. Finally, the SDT maintains the Galileo interface to NASA's Planetary Data System for archiving all science and ancillary data products for use by future generations of scientists, students, and the general public. Ultimately, the data gathered by Galileo is part of the legacy of Galileo to the world. Pat Lynn is the archive engineer and Galileo SDT interface to the PDS, succeeding past SDT member Diane Conner.
Developing the eclectic mix of equipment, software, and capabilities has been a hallmark of the SDT since its inception. Funding has always been tight, particularly during the 6-year-long cruise from Earth to Jupiter. However, Clarke convinced equipment suppliers of the glory of the Galileo Earth encounters, and they literally competed with each other to loan their hardware and software products to Galileo and the SDT in order to be where history was being made. Thus, equipment loaned to the SDT during the two Earth encounters provided the SDT a cosmic laboratory for testing the evolving science data system design. Arrays of loaned hardware allowed scientists to monitor and process their data in real time at JPL during the Earth encounters.
Also, real-time science data gathered during Galileo's first Earth encounter, in December 1990, was graphically displayed at a major science conference in San Francisco. Similarly, loaned equipment and software allowed graphical display and exhibition of real-time science data and images at the Smithsonian Air and Space Museum in Washington, DC, during the second Earth encounter, in December 1992.
SDT team leader Ted Clarke parlayed GI-bill support from submarine service into a bachelors degree in English literature followed by a masters degree in physics. He has delivered outreach lectures on the Space Program since 1977, including lectures at all three military academies. He is a co-investigator on a NASA contract, called Windows to the Universe, to share images and space science with the public via the Internet and World Wide Web. Clarke's portion of the task is the cultural associations of space exploration. This includes the people throughout history who contributed to humanity's understanding of the cosmos, and myths of the gods and heroes for whom constellations and celestial bodies are named, as well as the art and literature that sprang from those myths.
Of his contributions to the Galileo mission, Clarke is proudest of his role in planning, lobbying for, and promoting the two Galileo Earth encounters. He was instrumental in getting the Earth rotation movie pictures scheduled into the first Earth encounter sequence and in bringing the second Earth encounter to the public at the Smithsonian Institution. In April 1994 Clarke was awarded the NASA Exceptional Service Medal for his science, technical, and outreach contributions to the Galileo Earth encounters.