Closing In On
Venus
(17 July 2008) Starting this week,
spacecraft controllers have been executing a series of manoeuvres to gradually
bring Venus Express closer to its host planet.
In its modified
orbit, the spacecraft will be able to observe unexplored regions and
investigate phenomena that were not within its reach before.
Venus Express is studying largely unknown phenomena in the Venusian atmosphere like never before. Its suite of instruments is also digging into the interaction between the solar wind and the planetary environment. In addition, the mission is gathering glimpses of the planet's surface, which is strictly coupled with its dense atmosphere. (courtesy: ESA (Image by AOES Medialab))
The operational manoeuvres to bring the
spacecraft closer will be executed through the month of July, settling it into
its new orbit by 4 August.
Until now, Venus Express has occupied a
highly eccentric polar orbit: at its closest point (pericentre), the spacecraft
is between 250 km and 400 km from the planet, and at its farthest (apocentre),
it is about 66,000 km away. The pericentre is located at 84°
north.
This eccentric orbit was designed to facilitate observation of
the southern hemisphere for extended periods, and of the northern hemisphere
and the northern polar region at closer distances.
The altitude of the
pericentre will now be lowered to between 185 and 300 km. This modification
will enable the following science advantages:
The lowering of the Venus Express orbit is
the first step in a more ambitious strategy, yet to be confirmed in its
entirety. The intention is to lower the spacecraft's orbit further into the
atmosphere, such that the drag on the spacecraft's body can be measured by the
on-board accelerometers.
As the next step, Venus Express may test
aerobraking, a technique where a spacecraft uses the force exerted by the
planet's atmosphere to decelerate and so significantly change its orbit in a
controlled manner.
(source: ESA)
