Tag: Venus Express

After eight years, the European Space Agency has officially ended the Venus Express mission.

After this month of ‘surfing’ in and out of the atmosphere at low altitudes, the lowest point of the orbit was raised again through a series of 15 small thruster burns, such that by 26 July it was back up to about 460 km, yielding an orbital period of just over 22 hours. The mission then continued in a reduced science phase, as the closest approach of the spacecraft to Venus steadily decreased again naturally under gravity.

Under the assumption that there was some propellant still remaining, a decision was taken to correct this natural decay with a new series of raising manoeuvres during 23–30 November, in an attempt to prolong the mission into 2015. However, full contact with Venus Express was lost on 28 November. Since then the telemetry and telecommand links had been partially re-established, but they were very unstable and only limited information could be retrieved.

The agency has decided that further attempts to contact the spacecraft would essentially be a wasted effort, and has closed the books on this very successful mission. The spacecraft itself will soon burn up in Venus’s atmosphere when its orbit decays.

Engineers have been struggling to maintain contact with Venus Express, and have only been able to establish contact for intermittent periods.

Europe’s Venus Express was launched in November 2005 and got to the second planet from the Sun in April 2006, on what was originally a two-year mission. Since then it has sent data streaming back from its polar orbit.

But the probe’s days are numbered, and last month the flight control team at the European Space Operations Centre (ESOC) at Darmstadt, Germany, reported loss of contact with it. According to ESA’s Venus Express blog, it is possible that the remaining fuel on board the spacecraft was exhausted during recent manoeuvres and that the spacecraft is no longer in a stable attitude (the spacecraft’s high-gain antenna must be kept pointed toward Earth to ensure reliable radio contact).

They have been able to get bits of telemetry from the craft, but since its fuel supply is almost gone the possibility of keeping it operating much longer is limited.

After spending a month dropping down deep into Venus’s atmosphere, engineers are now raising Venus Express’s orbit.

Thus routine science operations concluded on 15 May, and the spacecraft’s altitude was allowed to drop naturally from the effect of gravity, culminating in a month ‘surfing’ between 131 km and 135 km above the surface. Additional small thruster burns were used to drop the spacecraft to lower altitudes, reaching 130.2 km earlier this week. Tomorrow, it is expected to dip to 129.1 km.

After eight years orbiting Venus, the mission is finally ending. They will use the spacecraft’s thrusters to lift it back up to almost 500 kilometers, where they will then allow its orbit to naturally decay, eventually ending the mission when it burns up in the atmosphere. There is also the chance they will run out of fuel during these last burns, ending the mission slightly sooner.

After concluding eight years of science observations in orbit around Venus, Venus Express is about to begin a series of atmospheric plunges to test the engineering of aerobraking at the extreme.

They plan to dive into Venus’s hellish atmosphere as low as 80 miles, where they hope not only to get data about this little studied region but to also learn more about the engineering of aerobraking. The article also gives a nice overview of the knowledge that Venus Express gathered in the past eight years.