Smart 1

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Image:Smart28261.jpg Smart 1 or SMART-1 is a European Space Agency satellite that orbits around Earth's moon, Luna. "SMART" stands for Small Missions for Advanced Research in Technology.

1 Spacecraft Design
2 Mission
3 Flight
4 Important events and discoveries
5 External links

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Spacecraft Design

SMART-1 is a lightweight probe (at launch 815 pounds or 367 kg, reducing to 287 kg by using propellant), just one metre (approximately 3 feet) across. The total cost is a relatively low 110 million euros (126 million U.S. dollars). SMART-1 is part of the European Space Agency's strategy to build spaceships smaller and more cheaply than those of its American counterpart, NASA.

Its solar-powered plasma thruster (Solar Electric Primary Propulsion, SEPP) is a Hall effect thruster (PPS-1350). It is designed to give it more endurance than a space probe equipped with traditional chemical rockets. The onboard propellant reserve amounts to just 60 litres (2.1 cubic feet) of inert xenon, with a mass of 80 kg. The thrusters use an electrostatic field to project xenon ions at high velocity.

The specific impulse is 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) produces a delta-v of ca. 45 m/s, more than three times what a chemical rocket would produce.

1190 W is 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. Thus orbital maneuvers are not carried out in short bursts, as with chemical rockets, but very gradually, with on-time typically once every orbit for about one third to one half of the time (when spiralling out: at the perigee side). In its lifetime of 5,000 hours a total delta-v of 4 km/s is available, corresponding to a total impulse of 1.5 MN·s.

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Mission

As a part of "Small Missions for Advanced Research in Technology", SMART-1 will test new spacecraft technologies. The primary objective of SMART-1 is to test the solar-powered ion thruster. It will also be testing the miniaturized scientific instruments, which are thought to be more efficient. If successful, these technologies will be used on future ESA missions.

A secondary objective is to learn more information about the Moon, such as how it was created. SMART-1 will map 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 will also determine the Moon's chemical composition using X-ray spectroscopy. A specific goal is 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 is also mapping the Moon's Peaks of Eternal Light (PELs), eerie mountaintops which are permanently bathed in sunlight and surrounded by craters shaded in eternal darkness.

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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 SEPP to gradually spiral out during thirteen months.

You can see the orbit up to October 26, 2004 here, 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.

Summary of osculating geocentric orbital elements
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 [1], 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 [2], 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.

Summary of osculating selenocentric orbital elements
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, which is the currently predicted date of its impact on the surface of the Moon. [3]

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Important events and discoveries

Image:Europe and Africa smart1 20040615.jpg

Image:Fig2-410.jpg

June 17, 2004: SMART-1 took a test image of Earth with the camera that will 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.