SMART-1
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Template:Infobox Spacecraft SMART-1 was a Swedish-designed European Space Agency satellite that orbited around the Moon. It was launched on 27 September, 2003 at 23:14 UTC from the European Spaceport in Kourou. "SMART" stands for Small Missions for Advanced Research in Technology. On September 3, 2006 (0542 UTC), SMART-1 deliberately crashed into the Moon's surface, ending its mission.[1]
Spacecraft design
SMART-1 was about one metre (approximately 3 feet) across, and lightweight in comparison to other probes. Its launch mass was 367 kg or 815 pounds, of which 287 kg was non-propellant.
It was propelled by a solar-powered Hall effect thruster using xenon propellant, of which there were 80 kg (60 litres by volume) at launch. The thrusters used an electrostatic field to ionize the xenon and accelerate the ions to a high velocity. This ion engine setup achieved a specific impulse of 16.1 kN·s/kg (1640 seconds), more than three times the maximum for chemical rockets. Therefore 1 kg of propellant (1/350 to 1/300 of the total mass of the spacecraft) produced a delta-v of about 45 m/s.
The solar arrays made 1190 W available for powering the thruster, giving a nominal thrust of 68 mN, hence an acceleration of 0.2 mm/s² or 0.7 m/s per hour. As for all ion-engine powered craft, orbital maneuvers were not carried out in short bursts but very gradually. The particular trajectory taken by SMART-1 to the Moon required thrusting for about one third to one half of every orbit. When spiralling away from the Earth thrusting was done on the perigee part of the orbit. The total delta-v expected over the thrusting lifetime of 5,000 hours is about 4 km/s, corresponding to a total impulse of 1.5 MN·s.
As part of the European Space Agency's strategy to build very inexpensive and relatively small spaceships, the total cost of SMART-1 was a relatively small 110 million euros (about 126 million U.S. dollars).
SMART-1 was developed by the Swedish Space Corporation[2] and built by Saab Ericsson Space in Linköping[3] on behalf of ESA.
Mission
As a part of Small Missions for Advanced Research in Technology, SMART-1 tested new spacecraft technologies. The primary objective of SMART-1 was to test the solar-powered ion thruster. It also tested the miniaturized scientific instruments, which were thought to be more efficient.
A secondary objective was to gather more information about the Moon, such as how it was created. SMART-1 mapped the lunar surface by way of X-ray and infrared imaging, taking images from several different angles so that the Moon's surface can be mapped in three dimensions. It also determined the Moon's chemical composition using X-ray spectroscopy. A specific goal was to use infrared light to search for frozen water at the Moon's south pole, where some areas of the surface are never exposed to direct sunlight. It also mapped the Moon's Peaks of Eternal Light (PELs), mountaintops which are permanently bathed in sunlight and surrounded by craters shaded in eternal darkness.
Instruments
- AMIE - miniature colour camera for lunar imaging
- D-CIXS - X-ray telescope for the identification of chemical elements on the lunar surface
- SIR - infrared spectrometer
- XSM - X-ray solar monitor to study solar variability and to complement D-CIXS
Flight
SMART-1 was launched September 27, 2003 together with Insat 3E and eBird 1, by an Ariane 5 rocket from the Guiana Space Center in French Guiana. After 42 minutes it was released into a geostationary transfer orbit of 7035 × 42 223 km. From there it used its Solar Electric Primary Propulsion (SEPP) to gradually spiral out during thirteen months.
The orbit can be seen up to October 26, 2004 at moontoday.net, when the orbit was 179 718 × 305 214 km. On that date, after the 289th engine pulse, the SEPP had accumulated a total on-time of nearly 3648 hours out of a total flight time of 8000 hours, hence a little less than half of its total mission. It consumed about 58.8 kg of xenon and produced a delta-v of 2737 m/s (46.5 m/s per kg xenon, 0.75 m/s per hour on-time). It was powered on again on November 15 for a planned burn of 4.5 days to enter fully into lunar orbit. It took until February 2005 using the electric thruster to decelerate into the final orbit 300-3000 km above the Moon's surface.
| Epoch (UTC) | Perigee (km) | Apogee (km) | Eccentricity | Inclination (deg) (to Earth equator) |
Period (h) |
|---|---|---|---|---|---|
| September 27, 2003 | ~7 035 | ~42 223 | ~0,714 | ~6.9 | ~10.6833 |
| October 26, 2003, 21:20:00.0 | 8 687.994 | 44 178.401 | 0.671323 | 6.914596 | 11.880450 |
| November 16, 2003, 04:29:48.4 | 10 843.910 | 46 582.165 | 0.622335 | 6.861354 | 13.450152 |
| December 8, 2003, 06:41:47.6 | 13 390.351 | 49 369.049 | 0.573280 | 6.825455 | 15.366738 |
| December 29, 2003, 05:21:47.8 | 17 235.509 | 54 102.642 | 0.516794 | 6.847919 | 18.622855 |
| February 1, 2004, 22:46:08.6 | 20 690.564 | 65 869.222 | 0.521936 | 6.906311 | 24.890737 |
| March 1, 2004, 00:40:52.7 | 20 683.545 | 66 915.919 | 0.527770 | 6.979793 | 25.340528 |
| August 25, 2004, 00:00:00 | 37 791.261 | 240 824.363 | 0.728721 | 6.939815 | 143.738051 |
| October 1, 2004, 21:30:45.9 | 69 959.278 | 292 632.424 | 0.614115 | 12.477919 | 213.397970 |
| October 26, 2004, 06:12:40.9 | 179 717.894 | 305 214.126 | 0.258791 | 20.591807 | 330.053834 |
After its last perigee on November 2,[4] on November 11, 2004 it passed through the L1 Lagrangian Point and into the area dominated by the Moon's gravitational influence, and at 1748 UT on November 15 passed the first periselene of its lunar orbit. The osculating orbit on that date was 6704 × 53 208 km,[5] with an orbital period of 129 hours, although the actual orbit was accomplished in only 89 hours. This illustrates the significant impact that the engine burns have on the orbit and marks the meaning of the osculating orbit, which is the orbit that would be travelled by the spacecraft if at that instant all perturbations, including thrust, would cease.
| Epoch (UTC) | Periselene (km) | Aposelene (km) | Eccentricity | Inclination (deg) (to Moon equator) |
Period (h) |
|---|---|---|---|---|---|
| November 15, 2004, 17:47:12.1 | 6 700.720 | 53 215.151 | 0.776329 | 81.085 | 129.247777 |
| December 4, 2004 10:37:47.3 | 5 454.925 | 20 713.095 | 0.583085 | 83.035 | 37.304959 |
| January 9, 2005, 15:24:55.0 | 2 751.511 | 6 941.359 | 0.432261 | 87.892 | 8.409861 |
| February 28, 2005, 05:18:39.9 | 2 208.659 | 4 618.220 | 0.352952 | 90.063603 | 4.970998 |
| April 25, 2005, 08:19:05.4 | 2 283.738 | 4 523.111 | 0.328988 | 90.141407 | 4.949137 |
| May 16, 2005, 09:08:52.9 | 2 291.250 | 4 515.857 | 0.326807 | 89.734929 | 4.949919 |
| June 20, 2005, 10:21:37.1 | 2 256.090 | 4 549.196 | 0.336960 | 90.232619 | 4.947432 |
| July 18, 2005, 11:14:28.0 | 2 204.645 | 4 600.376 | 0.352054 | 90.263741 | 4.947143 |
ESA announced on February 15, 2005, the endorsement of a proposal to extend the mission of SMART-1 by one year until August 2006. This date was later shifted to September 3, 2006, to "favour scientific observations from Earth".[6]
Lunar impact
SMART-1 impacted the Moon's surface as planned, on September 3, 2006 at 05:42:22 UTC, ending its mission. Moving at approximately 2000 m/s (4473 mph), SMART-1 created an impact visible with ground telescopes from Earth. It is hoped that not only will this provide some data simulating a meteor impact, but also that it might expose materials in the ground, like water ice, to spectroscopic analysis.
ESA estimated that impact ocurred at 34°24′S 46°12′W / 34.400°S 46.200°W. [7]These numbers can be entered into NASA's World Wind, to see where on the Moon it crashed. At the time of impact, the Moon was visible in North and South America, and places in the Pacific Ocean, but not Europe, Africa, or western Asia.
Important events and discoveries
- September 27, 2003: SMART-1 launched from the European Spaceport in Kourou by an Ariane 5 launcher.
- June 17, 2004: SMART-1 took a test image of Earth with the camera that would later be used for Moon closeup pictures. It shows parts of Europe and Africa. It was taken on May 21 with the AMIE camera, a compact imaging device with a weight of 450 grams.
- November 2, 2004: Last perigee of Earth orbit.
- November 15, 2004: First perilune of lunar orbit.
- January 15, 2005: Calcium detected in Mare Crisium.
- January 26, 2005: First close up pictures of the lunar surface sent back.
- February 27, 2005: Reached final orbit around the Moon with an orbital period of about 5 hours.
- April 15, 2005: The search for PELs begins.
- June 8, 2005: ESA announces that calcium was detected on the Moon.
- September 3, 2006: Mission ends with a planned crash into the Moon during orbit number 2890. [8]
References
- ^ http://news.bbc.co.uk/1/hi/sci/tech/5309656.stm
- ^ http://www.ssc.se/default.asp?groupid=2004121510349606
- ^ http://www.dn.se/DNet/jsp/polopoly.jsp?d=597&a=569860&previousRenderType=6
- ^ http://www.moontoday.net/news/viewsr.html?pid=14345
- ^ http://www.moontoday.net/news/viewsr.html?pid=14573
- ^ http://www.esa.int/esaCP/SEMQFHL8IOE_index_0.html
- ^ http://www.esa.int/SPECIALS/SMART-1/SEMBY5BVLRE_0.html
- ^ http://www.esa.int/SPECIALS/SMART-1/SEMV386LARE_0.html