Dr. Marc Rayman's Mission Log

  December 9, 1998

Mission Update:

Thank you for visiting the Deep Space 1 mission status information site, frequently referred to as one of the most popular logged sources of information between the Sun and the asteroid belt on this technology validation mission. This message was logged in at 12:45 pm Pacific Time on Wednesday, December 9.

After two weeks of uninterrupted thrusting, DS1's ion propulsion system was commanded off yesterday afternoon so that other activities could be conducted with the spacecraft. During the time that this revolutionary propulsion system was on, it changed DS1's speed by about 450 kilometers per hour, or about 280 miles per hour. At the throttle level at which the spacecraft has been for the last week, each day of thrusting added over 45 kilometers per hour, or about 30 mph. The power of ion propulsion is the terrifically low propellant consumption. During the past two weeks of operation, the spacecraft expended only about 2 kilograms of xenon, or less than 5 pounds.

After the ion propulsion system was turned off, the spacecraft successfully executed a complex pirouette to prepare it for other activities. The first was the activation of another advanced technology, known as PEPE, or the Plasma Experiment for Planetary Exploration. This device measures charged particles in space, both electrons and charged atoms, or ions. A special alignment was required to assure that the solar wind, the stream of charged particles flowing from the Sun, would not interfere with the sensitive instrument while it is being commissioned. Later on, however, it will make detailed measurements of that same solar wind. The device combines several functions into a unit of lower mass and lower power consumption than on traditional science missions. The activation of PEPE is very complex and while it was begun yesterday, it will not be completed until Thursday. In the meantime, however, yesterday's partial activation shows that its electron sensor works extremely well. Today's work will focus on the portions of the instrument to measure ions. PEPE was developed by the Southwest Research Institute in San Antonio and the Los Alamos National Laboratory. The testing of PEPE on DS1 is another step in preparing NASA for its future of smaller, less expensive missions to explore the solar system.

Following the work on PEPE, DS1 conducted telecommunications tests overnight. These tests were scheduled when the spacecraft was within view of a Deep Space Network antenna in Goldstone California. NASA also has antennas in Madrid, Spain and near Canberra, Australia for communicating with probes in deep space, but only certain antennas at Goldstone are capable of receiving the special signals DS1 radiated. The DSN and DS1 had planned an extremely ambitious set of activities which proceeded very very smoothly. DS1 used another of its advanced technologies, a very small, lightweight amplifier for radio signals at a frequency about 4 times higher than the current standard frequency used for deep-space missions. This frequency band, meaninglessly called Ka-band, is like another channel in the radio spectrum and offers the possibility of sending more information with less power, important for future small but capable spacecraft. The preliminary view of the vast volume of data collected last night shows that the generation and transmission of these signals worked as hoped on the spacecraft, and the reception and processing of the signals at the DSN was similarly successful. DS1 also put the main portion of its radio system through further tests, and it continued to operate as planned. That unit, built by Motorola and known by the inspiring appellation Small Deep Space Transponder, combines many functions normally performed by separate elements into one low mass unit.

Each NASA mission has a well documented set of objectives that must be satisfied. On December 2, DS1 met the criteria for minimum mission success. That was achieved by completing 200 hours of thrusting with the ion propulsion system and collecting extensive data on the performance of the advanced solar array, provided by BMDO, and the transponder. While other important experiments on these and other technologies lie ahead, the mission now ranks as another success in NASA's long and impressive history of travels beyond Earth orbit.

Deep Space 1 is now more than 19 times as far away from Earth as the moon. Radio signals, traveling at the universal limit of the speed of light, take about 50 seconds to make the round trip.

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