Artist's concept of SMART-1 nearing the moon. Photo: ESA

The European Space Agency (ESA) and the Swedish Space Corporation (SSC) signed on December 1 the contract for the development by SSC of the SMART-1 spacecraft to be used in a science and technology mission to the Moon in about three years time. The contract value is about 33 million Euros.

SMART-1 will test solar electric primary propulsion in preparation for future European interplanetary missions. The spacecraft will also carry cameras and other instruments for observing the lunar surface. SSC will use the most modern techniques for software and avionics development for SMART-1. This includes the use of automatic code generation for software and the extremely fault-tolerant CAN data bus from the automotive industry for internal data links in the spacecraft.

SSC's president, Dan Jangblad, says in a comment to the contract: "SMART-1 is a large step for SSC and a giant leap for Swedish space industry in that ESA is entrusting the prime contractor role for a European spacecraft to a Swedish company. SSC builds on its experience from the successful national Swedish satellite program and will now be able further develop this experience in a still more challenging context. I see SMART-1 making SSC and other Swedish space enterprises still more interesting partners and contractors on the world space market. The fact that the mission target is the Moon will serve as an additional inspiration to our team in its effort to make SMART-1 a success that all Europeans can be proud of."

Background
ESA's space science programme encompasses, in addition to the ambitious so-called Cornerstone and medium-sized missions, also small, relatively low-cost missions to test critical technology to be used in bigger projects. These small missions have been given the generic name SMART - "Small Missions for Advanced Research and Technology".

Artist's concept of SMART-1 spacecraft. Photo: ESA

The first mission in this programme, SMART-1, will test the use of solar electric primary propulsion for deep space missions such as the exploration of the planet Mercury. In addition to this technical test, SMART-1 will carry a scientific payload. ESA has chosen the Moon as the target for the flight. The spacecraft will be equipped with a miniature imager for lunar surface imaging, an infrared spectrometer for planetary geology, an imaging X-ray spectrometer for surface elemental composition as well as space plasma instruments including a Swedish Langmuir probe. The space plasma instruments will be used to characterise the effect on the spacecraft environment caused by the electric thruster.

On request from ESA and with the support of the Swedish National Space Board the SMART-1 feasibility study commenced during the second half of 1997. From the spring of 1998 until early summer 1999 a system definition study was carried out by SSC and the proposal for development of the spacecraft was submitted to ESA by SSC on July 12, 1999. ESA's tender evaluation board judged the proposal adequate in a decision in August and ESA's Science programme Committee approved the project and its budget during its meeting in Naples on September 22. The Industrial Policy Committee approved the Executive's procurement proposal during its meeting on September 30.

SSC's organization for SMART-1
SSC's project team for SMART-1 will be about 20 persons augmented by staff provided by consultant companies in Sweden and the UK. SSC's project manager is Mr Peter Rathsman, a veteran of satellite projects within SSC since 16 years, including the company's successful Freja plasma physics research satellite launched from China in 1992.

Technical approach
SMART-1 has the shape of a 1 x 1 x 1-meter cube. It will have a mass of no more than 350 kg and will be launched into a geostationary transfer orbit as a piggyback passenger on an Ariane 5 rocket. The PPS-1350 Plasma Hall thruster from the SEP division of Snecma provides a thrust of approximately 70 milliNewtons (the force that a 7-gramme letter exerts on your desk). The thruster expands the initial orbit during a 15 to 17 month period so that the Moon's gravitational field captures the spacecraft.

Artist's concept of SMART-1 entering orbit around the moon. Photo: ESA

The electric thruster will put the spacecraft into a polar orbit around the Moon between 1000 and 10,000-km altitude. The lunar orbit phase of the mission will last at least six months. The spacecraft will be controlled from the European Space Operations Centre (ESOC) in Darmstadt, Germany and supported by the Agency's ground stations in Spain, French Guyana, Belgium and Australia.

The solar panels will use gallium-arsenide cells and deliver about 1800 Watts of power. The spacecraft is three-axis stabilised using reaction wheels, star-trackers and sun sensors. Lithium-ion batteries will be used for energy storage.

The spacecraft avionics has been designed by SSC in close co-operation with ESTEC and is based on the ERC-32 SPARC microprocessor. On-board software will be coded in C++ and modern tools for automatic code generation will be used in its development. The data bus architecture selected is the CAN-bus, a robust system developed by the automotive industry.