Deep Space 1 (DS 1)

Launch data: Designation  25508 / 98061A Launch date  24 Oct 1998 - 12:08 UT Launch site  CC, LC-17A Launch vehicle  Delta-7326-9.5 (#D261) Mission  Asteroid-Flyby Operator   Heliocentric orbit Perihelion / Aphelion   Incl. to ecliptic   ° Period   min

Deep Space 1 - Credit: NASA.

Spacecraft data: Prime contractor  JPL & Spectrum Astro Customer  JPL Platform  SA-200HP bus Mass at launch  486.3 kg (including 81.5 kg of Xe and 31.1 kg of hydrazine) Dry Mass   kg Basic shape   Dimension  2.5 m high, 2.1 m deep, and 1.7 m wide Solar array  two solar panel, span= 11.75m Stabilization   DC power  2300 W Design lifetime

Description:

• The Deep Space 1 (DS1) was the first of a series of technology demonstration probes being developed by NASA's New Millennium Program. The spacecraft was to fly by asteroid 1992 KD and possibly comets Wilson-Harrington and Borrelly. Along with the technology demonstrations, the probe carried the Miniature Integrated Camera-Spectrometer (MICAS), an instrument combining two visible imaging channels with UV and IR spectrometers. MICAS was used to study the chemical composition, geomorphology, size, spin-state, and atmosphere of the target objects. It also carried the Plasma Experiment for Planetary Exploration (PEPE), an ion and electron spectrometer which will measure the solar wind during cruise, the interaction of the solar wind with target bodies during encounters, and the composition of the cometary coma.
• Spacecraft and Subsystems:
  The Deep Space 1 spacecraft was built on an octagonal aluminum frame, 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. The probe was powered by batteries and two solar panel "wings" attached to the sides of the frame which span roughly 11.75 m when deployed. 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 4 160 cm x 113 cm panels. The array furnished 2300 W at 100 volts at the beginning of the mission, and less as the spacecraft moved further from the Sun and 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.
• Propulsion 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 was 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 75 kg was expected to be used during the primary mission. Other technologies tested on this mission included a solar concentrator array, autonomous navigation plus two other autonomy experiments, small transponder, Ka-band solid state power amplifier, and experiments in low power electronics, power switching, and multifunctional structures (in which electronics, cabling, and thermal control were integrated into a load bearing element).

Mission details:

• Deep Space 1 was sucessfully launched from pad 17-A at the Cape Canaveral Air Station at 12:08 UT (8:08 a.m. EDT), the first launch under NASA's Med-Lite booster program, on a Delta 7326-9.5 with three strap-on solid propellant rockets. The Delta 7326 used three Alliant GEM-40 solid strap-on motors, the standard Delta II core vehicle, and a Thiokol Star 37FM solid motor as the third stage.
• Delta entered a 185 km parking orbit, then fired again to enter a 174 x 2744 km x 28.5 deg orbit. The third stage separated and accelerated to solar orbit with DS1, while the second stage burned again to a planned 556 x 1042 km x 31.5 deg orbit with SEDSAT.
• At 13:01 UT the third stage burn put DS1 into its solar orbit trajectory. DS1 separated from the Delta II about 550 km above the Indian Ocean. Telemetry was recieved by the NASA Deep Space Network 1 hour, 37 minutes after launch, a 13 minute delay from the expected time. The Star 37FM then separated and accelerated to place Deep Space 1 to escape velocity. The primary mission of Deep Space 1 probe was to test new technology for future interplanetary spacecraft, the main experiment being an ion propulsion engine using xenon propellant.
• DS1 was injected into a 0.99 x 1.32 AU x 0.4 deg solar orbit. (1 AU = mean Earth orbit radius = 149.6 million km).
• Deep Space 1 successfully started its ion engine on November 24, 1998 after an initial attempt failed after four minutes on November 10.
  This is the first time ion propulsion has been used as the primary propulsion on a spacecraft.
• From its initial solar orbit of 0.99 AU x 1.32 AU x 0.4 degree, Deep Space 1 was to fly past the 3 km diameter asteroid 1992 KD at its perihelion of 1.33 AU.
• Deep Space 1 made a flyby of minor planet (9969) Braille at 04:46 UTC on Jul 29, 1999. Flyby distance was less than 25 km and possibly as little as 15 km. DS 1 failed to point its camera to image the target at closest approach, but the navigation system was successful in bringing the vehicle close to the asteroid, and longer range IR imaging was successful. The NSTAR ion engine continues to operate well.
• A third burn phase in Jul-Oct 1999 raised perihelion by 10 million km more, and lowered inclination to 0.2 deg. In the meantime, on Sep 18 DS1 had successfuly completed its primary mission. The failure of DS1's star tracker soon afterwards left a follow-on mission in doubt - without the star tracker, DS1 did not know which way it was pointing, which makes it hard to steer. In a remarkable success for JPL, the DS1 team reprogrammed the spacecraft to use images from its MICAS science camera - with a field of view a hundred times smaller than the star tracker - and reformat them into a data stream compatible with the navigation system. They were helped by one of DS1's advanced technology tests, an autonomous navigation software package that used MICAS data, but its processing is only the first step in a long chain of software, so it's darn impressive that they managed to make it work. They can only fire the ion engine in directions where they can see an appropriately bright guide star in the MICAS. Developing a way of navigating using as few stars as possible was another challenge: only half a dozen will be needed for its new target, comet 19P/Borrelly, which requires a much bigger orbit change than the earlier burns. The trajectory can be fine-tuned by changing the date on which one star is replaced by another. After a massive effort, all was ready by June 2000, with the ion engine starting again on Jun 28. DS1 will encounter comet 19P/Borrelly in Sep 2001.
• DS1 Orbital Data:

   Date          Period Perihelion x Aphelion x Incl
   1998 Nov 10   446.6d 0.990 x 1.287 AU x 0.37 deg
   1999 Jan 22   459.5d 0.990 x 1.331 AU x 0.38 deg
   1999 Apr 27   470.4d 1.022 x 1.336 AU x 0.26 deg
   1999 Oct 27   492.6d 1.090 x 1.342 AU x 0.19 deg
   2001 Feb     (564.9d 1.287 x 1.378 AU x 0.20 deg) planned
   2001 May     (584.8d 1.291 x 1.436 AU x 0.21 deg) planned
  

  Perihelia: Oct 1998, Feb 2000, May 2001.
• Deep Space 1 has completed its flyby of comet 19P/Borrelly. The spacecraft flew past the nucleus at a distance of 2200 km at 2230 UTC on Sep 22, 2001 and appears to have survived the encounter in good shape, sending back photos of the comet. DS1 is in a roughly 1.3 x 1.5 AU x 0 deg (ecliptic) orbit; Borrelly's orbit is 1.3 x 5.9 AU.
• The Deep Space 1 probe was turned off on Dec 18, 2001 completing an incredibly successful technology proving mission. DS1's orbit is about 1.30 x 1.44AU x 0.22 deg. DS1's ion drive technology will be used for the Dawn asteroid orbiter mission which has just been selected for NASA's Discovery program.
• SEDSAT (25509 / 98061B)

External links:

• EOportal.org Satellite description