Deep-Space-1 was a space probe launched by NASA on 24 October 1998. The spacecraft, lifted into space that day by a Delta rocket, carried twelve new technologies, which were designed for deep-space usage. The mission objectives were to try out all the technologies that might have a function in deep-space exploration all in one craft and so save the cost of multiple testing missions.
The first of these technologies was the ion propulsion drive. This drive used the gas xenon, which was ionized by an electrical charge. The ions were then expelled as a controlled discharge to propel the craft. While considered too slow for near earth missions, this type of drive is suitable for extended un-manned missions to the asteroid belt and the near sun planets. This innovative propulsion system worked in excess of expectations and set a record for the length of time that a spacecraft’s propulsion system was in operation.
The power for the craft was derived from a unique solar array. This used 720 lenses to concentrate the sun’s energy on 3600 solar cells. Although only producing 3500 watts at the same distance from the sun as the earth this might not seem much it was in excess of any other spacecraft at the time and successfully powered the craft throughout its extended mission.
Usually the course of an un-manned spacecraft is controlled totally from mission control but Deep-space-1 was equipped with an auto-navigation system. The auto-nav would switch on once a week and by examining a series of images of near objects along with the stars would plot its position. It would then make any necessary changes to its course. To carry out these functions, the auto-nav had to know how much power was available to activate the ion drive while still maintaining the essential equipment on the craft working. These calculations became more critical as the craft got further away from the sun because the amount of power produced by the solar array decreased and the power required to heat the craft increased. The auto-nav system was another technology that performed in excess of expectations allowing the mission to be extended.
Power consumption and weight are important aspects of an extended space mission. Deep-Space-1 incorporated unique lightweight low power microelectronics. These devices, using very low voltage combined with low capacitance, again worked throughout the extended mission.
NASA has been trying to reduce the size of spacecraft used for space exploration. To do this they had to design smaller equipment. Deep-Space-1 had a combined camera and spectrometer known as MICAS, which replaced three conventional pieces of equipment. This package consisted of two black and white cameras along with imaging spectrometers for both the ultra-violet and infrared parts of the spectrum. The equipment had no moving parts with the shutters on individual systems activating electronically. All but the ultra-violet spectrometer functioned as expected. The primary mission objective was the testing of the new technologies, so the scientists considered even this small failure a success.
The Plasma Experiment for Planetary Exploration (PEPE) was another success. This lightweight low power system examined plasma interactions and the solar wind. It was quarter the weight and used less than half the power of a similar system used on the Cassini mission.
The craft carried a deep space transponder designed to allow tracking of multiple missions in space. This again was a successful test of new technology.
A solid-state Ka-ban amplifier allowed the sending of radio signals at a frequency four times greater than that used on previous missions. The amplifier was again a lightweight system that was very successful.
Deep-Space-1 successfully used a beacon monitoring system to communicate with mission control. Having monitored the health of the craft it would send out one of four signals to inform mission control how urgently it required access to the resources of the Deep-Space Network. The network resources are limited so such a system allowed their economical usage.
There was an artificial intelligence system on board to plan and execute spacecraft functions. This autonomous remote system formulated its own plans based on the objectives set by the mission control team. Having the spacecraft control itself was a unique but successful innovation freeing up many man-hours for the mission control team.
Another test carried out successfully by the craft was of a power actuating and switching module. This module would report to the on board computer how much power was being switched and the system using the power.
A multifunctional structure was tested for the crafts electronics system. This also allowed control over the ships temperature. The success of this feature has implications on the design of future spacecraft electronic systems.
With all the primary mission objectives of testing the innovative systems completed, the mission control team applied to NASA to send the craft on an extended mission to meet with a comet. With this mission approved, on 28 June 2000, Deep-Space-1 was sent to meet the comet Borrelly. To carry out the extended mission MICAS was reconfigured as a star tracker. The craft had a few problems on the journey twice its navigational systems were scrambled by solar storms and once MICAS got a fix on a star that was too dim for accurate navigation. The mission control team was able to get the craft back on course all three times. On September 22 2001, it took some of the best photographs of a comet ever taken and sent back these along with other valuable data on comet Borrelly to mission control.
On December 18 2001, Deep-Space-1 was retired and now drifts in space. The mission was a greater success than ever could have been envisioned. Not only did nearly all of the technology work within or even better than expectations; the craft outlived its expected mission then went on to complete a totally unexpected task.
