Source: nasa.gov
10-20-2007 15:04
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On-orbit Dry Mass: 305 kg
Description
The SMART-1 spacecraft impacted the Moon as planned on Sunday, 3 September, at 5:42 UT (1:42 a.m. EDT).
The SMART-1 (Small Missions for Advanced Research in Technology 1) is a lunar orbiter designed to test spacecraft technologies for future missions. It entered initial lunar orbit on 13 November 2004. The primary technology being tested is a solar-powered ion drive. It will also carry an experimental deep-space telecommunications system and an instrument payload to monitor the ion drive and study the Moon. The primary scientific objectives of the mission are to return data on the geology, morphology, topography, mineralogy, geochemistry, and exospheric environment of the Moon in order to answer questions about planetary formation accretional processes, origin of the Earth-Moon system, the lunar near/far side dichotomy, long-term volcanic and tectonic activity, thermal and dynamical processes involved in lunar evolution, and water ice and external processes on the surface.
Spacecraft and Subsystems
SMART-1 is a box-shaped spacecraft roughly a meter on a side with two large solar panel wings spanning 14 meters extending from opposite sides. The launch mass, including fuel, is 366.5 kg, the mass at the time it reaches the Moon should be about 305 kg. A solar-electric propulsion system (a Stationary Plasma Hall-effect thruster, PPS-1350) uses xenon gas as a propellant by ionizing the xenon and accelerating and discharging the plasma from the spacecraft at high speed. Electrons are also released into the flow to maintain a neutral charge on the spacecraft. A thrust of 70 milliNewtons and a specific impulse of 1600 s is produced. 82 kg of supercritical xenon propellant will be carried aboard SMART-1 in a tank mounted in the center of the structure above the thruster. The spacecraft is three-axis stabilized using four skewed reaction wheels and eight 1-N hydrazine thrusters mounted on the corners of the spacecraft bus. Attitude knowledge is provided by a star tracker, sun sensor, and angular rate sensors.
1850 W of power is produced from an array of gallium-indium-phosphide gallium arsenide germanium (GaInP/GaAs/Ge) solar cells covering an active surface on the wings of about 10 square meters. Solar array power is regulated to 50 V in the power control and distribution unit and distributed via solid-state power controllers. Power is stored in five 130-Whr lithium ion battery cells. Roughly 75% of the power is used to run the propulsion system during flight. Thermal control is achieved through the use of radiators, heat pipes, multilayer insulation blankets, thermistor controlled heaters, and high emissivity optical properties. Communication takes place via a medium gain and two low gain S-band antennas as well as the antenna for the experimental Ka/X system. The medium gain antenna provides a telemetry rate of 65 kb/s. The two low gain antennas provide omin-directional ground coverage at 2 kb/s. The medium gain, Ka/X band, and one low gain antenna are mounted on one side panel of the spacecraft bus and the other low gain antenna is mounted on the opposite panel.
The spacecraft will carry a suite of science and technology instruments with a total mass of 19 kg. The science instruments include a pan-chromatic camera (AMIE) for lunar imaging, Langmuir probes mounted on booms (SPEDE) to measure the plasma environment, and radio science experiments (RSIS). Science instruments which are being tested as part of the technology verification are a miniaturized visible/near-infrared spectrometer (SIR) for lunar crustal studies, a miniature X-ray spectrometer for astronomy and lunar chemistry (D-CIXS), and an X-ray spectrometer to calibrate D-CIXS and to study the Sun (XSM). The Electric Propulsion Diagnostic package (EPDP) is a multi-sensor suite designed specifically to monitor the ion propulsion system, it also works in concert with the SPEDE to study the space plasma environment. The RSIS is also used to monitor the ion propulsion system. Finally an experimental telecommunication and tracking system, the Ka/X-band TTC (Telemetry and Telecommand) Experiment (KaTE) is included in the payload for technology assessment. The AMIE camera will also be used to support a test of an image-based On-Board Autonomous Navigation (OBAN) system. OBAN is designed to minimize the amount of ground intervention required for the mission.
Mission Profile
The SMART-1 spacecraft launched on 27 September 2003 from Kourou, French Guiana as an auxiliary passenger on an Ariane-5 Cyclade which launched two other large satellites as its primary payload. It was put into a geostationary transfer orbit, 742 x 36,016 km, inclined at 7 degrees to the equator. The spacecraft used its ion drive over a period of 14 months to elongate its Earth orbit and utilized three lunar resonance maneuvers in August, September, and October 2004 to minimize propellant use. Its final continuous thrust maneuver took place over 100 hours from 10 to 14 October 2004. Lunar orbit capture occurred on 13 November 2004 at a distance of 60,000 km from the lunar surface. The ion engine began firing in orbit at 05:24 UT (12:24 a.m. EST) on 15 November to start a 4.5 day period of thrust to lower the orbit. The first perilune took place on 15 November at 17:48 UTC (12:48 p.m. EST) at an altitude of about 5000 km above the lunar surface. The engine was then used to lower the initial 4962 x 51477 km altitude, 5 day, 9 hour period, 81 degree inclination orbit, putting SMART-1 into a 300 x 3000 km polar orbit. Lunar commissioning began in mid-January 2005 and lunar science operations in February 2005. The mission has been extended from its originally planned 6-month lifetime by a year, so it will now conduct mapping of the Moon's surface and evaluating the new technologies onboard from lunar orbit until August 2006. The xenon-ion engine was shut down in September 2005 after exhausting its fuel supply. It operated for almost 5000 hours and underwent 843 starts and stops. SMART-1 performed a controlled crash into the Moon at about 2 km/sec on 3 September 2006, at 5:42 UT in the mid-southern region of the near side of the Moon in Lacus Excellentiae (Lake of Excellence) at 34.4 S, 46.2 W. The total cost of the spacecraft is estimated at 100 million euros in 2001 economic conditions (~$90 million U.S.).
Editor:Liu Fang
