Instrument Host Overview
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   Deep Space 1 (DS1) was the first mission representing the NASA New
   Millennium program, which was chartered to validate in space
   advanced, high-risk technologies important for future space and
   Earth science programs.  The advanced technology payload tested on
   DS1 comprised solar electric propulsion, solar concentrator arrays,
   autonomous on-board navigation and other autonomous systems,
   several telecommunications and microelectronics devices, and two
   low-mass integrated science instrument packages.  The technology
   evaluations occurred during the primary mission phase and, with
   successful completion of these tasks, an extended mission devoted
   to scientific studies was approved.
 
 
   Spacecraft and Subsystems
 
   The Deep Space 1 spacecraft was built on an octagonal aluminum
   frame bus 1.1 x 1.1 x 1.5 m in size.  With instruments and systems
   attached, the spacecraft measured 2.5 m high, 2.1 m deep, and 1.7 m
   wide. The launch mass of the spacecraft was about 486.3 kg, which
   included 31.1 kg of hydrazine and 81.5 kg of xenon gas.
 
   Thermal control was accomplished with the standard multilayer
   insulation or thermal blanketing, as well as with electrical
   heaters and radiators.
 
   Attitude orientation sensing was achieved through the use of a star
   sensor, an inertial measurement unit (gyroscope) and a Sun sensor.
   Hydrazine thrusters were used for maintaining attitude control,
   with the spacecraft in three-axis stabilized mode.
 
   The probe was powered by a battery and two solar panel 'wings'.
   The battery was a 24 amp-hour nickel hydrogen battery, which
   provided power immediately after launch.  It also supplemented the
   solar array power during ion engine thrusting, to cover transients
   in the spacecraft's power consumption, and during periods when the
   solar arrays were pointed too far away from the sun to collect
   sufficient energy to run all of the spacecraft systems.  The solar
   panels, designated SCARLET II (Solar Concentrator Arrays with
   Refractive Linear Element Technology) constituted one of the
   technology tests on the spacecraft.  A cylindrical lens
   concentrated sunlight on a strip of GaInP2/GaAs/Ge photovoltaic
   cells and acted to protect the cells. Each solar array consisted of
   four 160 cm x 113 cm panels.  The array furnished 2500 W at 100
   volts at the beginning of the mission, but this level dropped as
   the spacecraft moved further from the Sun and as the solar cells
   aged.
 
   Communications were via a high-gain antenna, two low-gain antennae,
   and a Ka-band antenna, all mounted on top of the spacecraft.  A
   third low gain antenna was mounted on the bottom of the spacecraft.
   The Small Deep Space Transponder and the Ka-band Solid-State Power
   amplifier were two of the advanced technologies, allowing data to
   be sent over smaller antennas with less power than missions using
   the X-band.
 
   The propulsion system represented one of the advanced new
   technologies being validated.  Thrust was provided by a xenon ion
   engine mounted in the propulsion unit on the bottom of the frame.
   The 30 cm diameter engine consisted of an ionization chamber into
   which xenon gas is injected. Electrons were emitted by a cathode
   traverse discharge tube and collided with the xenon gas, stripping
   off electrons and creating positive ions. The ions were accelerated
   through a 1280 volt grid at to 31.5 km/sec and ejected from the
   spacecraft as an ion beam, producing 0.09 Newtons (0.02 pounds) of
   thrust at maximum power (2300 W) and 0.02 N at the minimum
   operational power of 500 W. The excess electrons were collected and
   injected into the ion beam to neutralize the electric charge. Of
   the 81.5 kg of xenon, approximately 17 kg were consumed during the
   primary mission.  Only low-levels of thrust are available from the
   ion engine, so separate hydrazine thrusters were used for attitude
   control and for situations where a rapid acceleration was required
   (e.g. last minute course corrections during an encounter).
 
   Because of the long-term thrusting of the ion engine, DS1 needed to
   take a different approach to navigation and decision-making, and in
   this vein, three of the advanced technologies dealt with spacecraft
   autonomy.  DS1 was able to find its location in the solar system by
   taking images of known asteroids and comparing their positions
   against the background stars.  Furthermore, it had advanced
   on-board decision-making capabilities and improved communications
   regarding spacecraft health.
 
   DS1 carried two different scientific instrument packages.  First,
   the Miniature Integrated Camera Spectrometer (MICAS) included a
   camera and an infrared imaging spectrometer.  MICAS also had an
   ultraviolet spectrometer, but this part of the instrument did not
   function properly.  Second, the Plasma Experiment for Planetary
   Exploration (PEPE) contained several instruments for studying space
   plasmas.  Not only was PEPE used to obtain scientific measurements
   of space plasmas during cruise phase and during the asteroid and
   comet encounters, but it was also used to determine the effects of
   the ion engine on the spacecraft, the instruments and the
   surrounding environment.
 
   Although there were 12 advanced technologies on Deep Space 1, the
   rest of the spacecraft was composed of current, low-cost components
   that have been tried and tested on other missions. (The Deep Space
   1 flight computer, for instance, was based on that used by Mars
   Pathfinder and other missions.) This approach was used because the
   focus of the New Millennium Program is on proving that certain
   advanced technologies work in space, not on building complete
   spacecraft representative of those to be used in future missions.
   Because of the high-risk, low cost aspect of the mission, there
   were no back-up systems to provide redundancy against the failure
   of major components.
 
   The 12 advanced technologies subjected to verification on DS1:
   Major spacecraft sub-systems
      1) Solar electric propulsion system
      2) Solar concentrator arrays
   Spacecraft autonomy:
      3) Autonomous onboard optical navigation
      4) Beacon monitor operations
      5) Autonomous remote agent
   Science instruments
      6) Miniature integrated camera and spectrometer  (MICAS)
      7) Plasma experiment for planetary exploration (PEPE)
   Telecommunications
      8) Small deep-space transponder
      9) Ka-band solid-state power amplifier
   Microelectronics
     10) Low-power electronics
     11) Power activation and switching modules
     12) Multifunctional structure