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Venus Express Reaches Final Mission Orbit
Darmstadt, Germany (SPX) May 10, 2006 ESA announced Tuesday the Venus Express spacecraft reached its operational orbit on Sunday, after completing 16 transitory loops around the veiled planet. ESA's ground station in New Norcia, Australia, received a transmission from the spacecraft at 9:49 p.m., indicating it would achieve the preplanned mission successfully about 18 hours later. Launched last Nov. 9, Venus Express arrived at its destination on April 11, after its journey through the inner solar system. The initial orbit, called a capture orbit, consisted of an ellipse ranging from 330,000 kilometers (205,000 miles) at its apocenter - or farthest point from the Venusian surface - to less than 400 kilometers (250 miles) at its pericenter, or closest point. After the nine-day capture orbit, Venus Express had to perform a series of maneuvers to reduce gradually the apocenter and pericenter altitudes. The spacecraft achieved this by firing its main engine twice - on April 20 and 23 - and using its banks of thrusters, which ignited five times (on April 15, 26 and 30, and May 3 and 6). "Firing at apocenter allows the spacecraft to control the altitude of the next pericenter, while firing at the pericenter controls the altitude of the following apocenter," explained Andrea Accomazzo, spacecraft operations manager at ESA's European Space Operations Center. "It is through this series of operations that we reached the final orbit last Sunday, about one orbital revolution after the last pericenter change maneuver on Saturday." Venus Express entered its target orbit at apocenter on Sunday at 3:31 p.m. Central European Time, when the spacecraft was at 151 million kilometers (94 million miles) from Earth. Now, the spacecraft is running on an ellipse substantially closer to the planet than during the initial orbit. The science orbit ranges from 66,000 to 250 kilometers (41,000 to 155 miles) over Venus and runs along a polar trajectory. The new pericenter sits almost above the planet's north pole, at 80 degrees north latitude, and it takes 24 hours for the spacecraft to travel around the planet. "This is the orbit designed to perform the best possible observations of Venus, given the scientific objectives of the mission," said H�kan Svedhem, Venus Express project scientist. "These include global observations of the Venusian atmosphere, of the surface characteristics and of the interaction of the planetary environment with the solar wind. It allows detailed high resolution observations near pericenter and the north pole, and it lets us study the very little explored region around the south pole for long durations at a medium scale." Until early next month, Venus Express will continue its orbit commissioning phase, which started on April 22. "The spacecraft instruments are now being switched on one by one for detailed checking, which we will continue until mid May," said Don McCoy, the spacecraft's project manager. "Then we will operate them all together or in groups. This allows simultaneous observations of phenomena to be tested, to be ready when Venus Express' nominal science phase begins on June 4." Related Links Venus Express
Venus Express Transmits First Images
Darmstadt, Germany (SPX) Apr 17, 2006ESA's Venus Express orbiter returned its first images of the veiled planet Wednesday, beginning with a striking view of the Venusian south pole in both visible and infrared light. |
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