ESA's SMART-1 spacecraft is now in its 176th orbit, and is in good health with all functions performing well. The first major mission target, to leave the most dangerous part of the radiation belts which surround the Earth, has been achieved.
Between 23 December 2003 and 2 January 2004, the electric propulsion system ('ion engine') fired continuously for a record duration of more than 240 hours. This is likely to remain the record for some time because, later in January, SMART-1 changes from continuous thrusting to more orbitally-efficient periodic firing.
The total cumulated thrust time so far is more than 1500 hours, and the engine has consumed 24 kilograms of xenon propellant gas. This has now raised the speed of the spacecraft to about 3850 kilometres per hour.
The spacecraft is travelling in a continuous spiral leading from one orbit to another, and it is currently passing closest to the Earth at about 20 000 kilometres, and travelling out to a distance of nearly 60 000 kilometres (its orbital period has almost been doubled from the initial 10 hours 41 minutes to the present 20 hours and 19 minutes).
SMART-1 is now in its 78th orbit and has been flying for the last week in an intense radiation environment, caused by the recent exceptional solar activity. The intense solar flares and associated 'coronal mass ejections' have generated extreme geomagnetic storms and SMART-1, like many other spacecraft, has had to endure this harsh environment.
Apart from some minor temporary disturbances to the on-board computer and the star tracker (used for navigation), the only effect of the intense solar activity has been a disruption to the operation of the 'ion' engine, used to boost SMART-1's orbit out towards the Moon. At one point, the ion engine automatically shut down, but restarted itself later with no problems. This is also a temporary condition and will disappear when the extreme solar activity subsides.
Despite this, SMART-1's ion engine has generated thrust for a total cumulative time of more than 380 hours and has used only about 6 kg of its xenon fuel. The ion engine actually provides about 1% higher thrust than that expected before launch. This confirms ESA's confidence in the excellent condition of the solar-electric propulsion system.
From the start of the engine's boosting, SMART-1 has now increased the lowest point of its orbit around the Earth out to 2960 kilometres, and the maximum distance to about 44 000 kilometres. It now takes about 12 hours to complete one revolution of Earth.
SMART-1’s journey to the Moon is now fully under way. After the initial test firing of the ion engine in Earth orbit, there was a series of further tests to measure the engine’s behaviour. These have now been completed.
At this time, the engine is being fired as planned for about 90% of each orbit to gradually raise it away from the Earth on its spiralling trip out to the Moon. The engine can’t be fired during certain parts of the orbit when the spacecraft is in the shadow of the Earth, because then the solar arrays will not generate electrical power.
Since its launch, the size of the spacecraft orbit has already increased by 500 kilometres and all systems on-board are functioning well. “As a newborn in space, SMART-1 is progressively waking up to its new environment,” said Bernard Foing, ESA’s SMART-1 Project Scientist. “Like caring parents, ESA engineers and scientists are monitoring its position, temperature and health signals around the clock.”
SMART-1’s scientific instruments are also in good health, and have been checked in what is called the ‘Pre-commissioning’ phase. Andrea Marini, ESA’s SMART-1 Payload Engineer said: “After these years of development and testing of the SMART-1 payload, what an emotional time it has been to be able to communicate with the instruments, and receive their signals as expected.”
As part of its mission objectives, SMART-1 is collecting interesting data about the behaviour of the ion engine during its passages (or 'transits') in and out of the Earth’s Van Allen radiation belts, which will continue for the next two months. These radiation belts surround the Earth with a stormy environment of energetic particles that could affect the electronic systems and computers on board the spacecraft.
The engine, however, is already working well in these transits. When SMART-1 is safely out of the Van Allen belts also its instruments will be able to operate fully and provide more sophisticated data. They will be calibrated to improve their vision in the visible, infrared and X-ray wavelengths, and to test further the technologies on board this clever space baby.
The launch of ESA’s SMART-1 spacecraft to the Moon onboard an Ariane 5 rocket from Kourou, French Guiana successfully took place on 28 September at 1 hour 14 Central European Summer Time. The satellite separated from the launcher 42 minutes after lift-off and was placed into a geostationary transfer orbit with 654 km perigee and 35.885 km apogee. First signals of the satellite were received 2 minutes later at 1 hour 58 over the Perth ground station in Western Australia. The solar arrays had both been deployed by 2 hours 24 local time. Telemetry received confirms a nominal satellite performance in all subsystems. The first Electric Propulsion Firing is planned for tomorrow, 30 September.
Separation of SMART-1 41:31 minutes into the flight.
Arianespace Flight 162 has lifted off from the Spaceport in French Guiana, carrying a three-satellite payload, including ESA's
01:17 CEST. Lift-off of Ariane 5 with SMART-1.
23:00 CEST. Everything is fine in the main control room of ESOC in Darmstadt. All systems are green - we are expecting the launch as planned. The SMART-1 flight team is relaxed, in the starting blocks, waiting for the launch of SMART-1 from Kourou.
16:00 CEST. Final preparations for tonight's liftoff of Flight 162 are nearly complete following yesterday's transfer of the Ariane 5 to the launch zone, reports Arianespace.
Last update: 5 October 2004