SMART-1

Smart1 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 Guiana Space Centre in Kourou, French Guiana. "SMART" stands for Small Missions for Advanced Research in Technology. On September 3, 2006 (05:42 UTC), SMART-1 was deliberately crashed into the Moon's surface, ending its mission.^[1]

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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 809 pounds, of which 287 kg (633 lb) was non-propellant.

It was propelled by a solar-powered Hall effect thruster (Snecma PPS-1350-G) using xenon propellant, of which there was 82 kg (50 litres by volume at a pressure of 150 bar) at launch. The thrusters used an electrostatic field to ionize the xenon and accelerate the ions to a high speed. This ion engine setup achieved a specific impulse of 16.1 kN·s/kg (1,640 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 thruster had a weight of 29 kg with a peak power consumption of 1,200 watts.^[2]

The solar arrays made 1,190 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 (i.e., just under 0.00002 g of acceleration). 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 designed and developed by the Swedish Space Corporation^[3] on behalf of ESA. Assembly of the spacecraft was carried out by Saab Ericsson Space in Linköping. Tests of the spacecraft were directed by Swedish Space Corporation and executed by Saab Ericsson Space.

The project manager at ESA was Giuseppe Racca and the project mananger at the Swedish Space Corporation was Peter Rathsman.

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. 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. SMART-1 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. SMART-1 also tested the use of miniaturized scientific instruments, which are considered more efficient.

SMART-1 ended its mission by being deliberately crashed onto the Moon's surface at 34.24° S 46.12° W. Scientists hope that the impact will have kicked up a large enough quantity of fresh lunar "soil" so that they may study its composition.

Instruments

AMIE

The Advanced Moon micro-Imager Experiment was a miniature colour camera for lunar imaging. The CCD camera with three filters of 750, 900 and 950 nm was able to take images with an average pixel resolution of 80 m (about 260 ft). The camera weighed 2.1 kg (about 4.5 lb) and had a power consumption of 9 watts. ^[4]

D-CIXS

The Demonstration of a Compact X-ray Spectrometer was an X-ray telescope for the identification of chemical elements on the lunar surface. It detected the x-ray fluorescence (XRF) of crystal compounds created through the interaction of the electron shell with the solar wind particles to measure the abundance of the three main components: magnesium, silicon and aluminium. The detection of iron, calcium and titanium depended on the solar activity. The detection range for x-rays was 0.5 to 10 keV. The spectrometer and XSM (described below) together weighed 5.2 kg and had a power consumption of 18 watts.

XSM

The X-ray solar monitor studied the solar variability to complement D-CIXS measurements.

SIR

The Smart-1 Infrared Spectrometer was an infrared spectrometer for the identification of mineral spectra of olivine and pyroxene. It detected wave lengths from 0.93 to 2.4 µm with 256 channels. The package weighed 2.3 kg and had a power consumption of 4.1 watts.^[5]

EPDP

The Electric Propulsion Diagnostic Package was to acquire data on the new propulsion system on SMART-1. The package weighed 0.8 kg and had a power consumption of 1.8 watts.^[6]

SPEDE

The Space Potential Electron and Dust Experiment. The experiment weighed 0.8 kg and had a power consumption of 1.8 watts. Its name was intentionally chosen so that its acronym is the same as the first name of Spede Pasanen, famous Finnish movie actor, movie producer, inventor etc.

KATE

K_a band TT&C (telemetry, tracking and control) Experiment. The experiment weighed 6.2 kg and had a power consumption of 26 watts.

Flight

SMART-1 was launched September 27, 2003 together with Insat 3E and eBird 1, by an Ariane 5 rocket from the Guiana Space Centre in French Guiana. After 42 minutes it was released into a geostationary transfer orbit of 7,035 × 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 3,648 hours out of a total flight time of 8,000 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 2,737 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 300-3,000 km above the Moon's surface.^[7]

After its last perigee on November 2,^[8] 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 6,704 × 53,208 km,^[9] 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.

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 enable scientific observations from Earth.^[10]

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 2,000 m/s (4,500 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 occurred at 34°24′S, 46°12′W. ^[11]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.

This project has generated data and know-how that will be used for other missions, such as the ESA's BepiColombo mission to Mercury.

The Committee on Space Research has established rules to protect planets and moons from possible contamination by spacecraft. In response to concerns of SMART-1 contaminating the Moon, ESA claims that "every chemical element present on SMART-1 and in its instruments exists naturally on the Moon".^[12]

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.
• 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.
• September 3, 2006: Mission ends with a planned crash into the Moon during orbit number 2,890. ^[13]

See also

• List of artificial objects on the Moon

References

1. ^ http://news.bbc.co.uk/1/hi/sci/tech/5309656.stm
2. ^ Kugelberg J., Bodin P., Persson S., Rathsman P. (2004). "Accommodating electric propulsion on SMART-1". Acta Astronautica 55: 121 – 130. doi:10.1016/j.actaastro.2004.04.003.
3. ^ http://www.ssc.se/default.asp?groupid=2004121510349606
4. ^ Josset J. L., Beauvivre S., Cerroni P., De Sanctis M. C., Pinet P., Chevrel S., Langevin Y., Barucci M. A., Plancke P., Koschny D., Almeida M., Sodnik Z., Mancuso S., Hoffmann B. A., Muinonen K., Shevchenko V., Shkuratov Y., Ehrenfreund P., Foing B. H. (2006). "Science objectives and first results from the SMART-1/AMIE multicolour micro-camera". Moon and Near-Earth Objects Advances in Space Science 37: 14-20.
5. ^ Basilevsky A. T., Keller H. U., Nathues A., Mall J., Hiesinger H., Rosiek M. (2004). "Scientific objectives and selection of targets for the SMART-1 Infrared Spectrometer (SIR)". Planetary and Space Science 52: 1261-1285. doi:10.1016/j.pss.2004.09.002.
6. ^ Di Cara D. M., Estublier D. (2005). "Smart-1: An analysis of flight data". Acta Astronautica 57 (2-8): 250-256. doi:10.1016/j.actaastro.2005.03.036.
7. ^ Rathsman P., Kugelberg J., Bodin P., Racca G. D., , Foing B., Stagnaro (2005). "SMART-1: Development and lessons learnt". Acta Astronautica 57 (2-8): 455-468. doi:10.1016/j.actaastro.2005.03.041.
8. ^ http://www.moontoday.net/news/viewsr.html?pid=14345
9. ^ http://www.moontoday.net/news/viewsr.html?pid=14573
10. ^ http://www.esa.int/esaCP/SEMQFHL8IOE_index_0.html
11. ^ http://www.esa.int/SPECIALS/SMART-1/SEMBY5BVLRE_0.html
12. ^ ESA SMART-1 Impact FAQ, Q.8&9
13. ^ http://www.esa.int/SPECIALS/SMART-1/SEMV386LARE_0.html

• Kaydash V., Kreslavsky M., Shkuratov Yu., Gerasimenko S., Pinet P., Chevrel S., Josset J.-L., Beauvivre S., Almeida M., Foing B. (2007). "PHOTOMETRIC CHARACTERIZATION OF SELECTED LUNAR SITES BY SMART-1 AMIE DATA". Lunar Planetary Science, XXXVIII, abstract 1535, http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1535.pdf].