The VENµS satellite has two missions, a scientific mission that requires to have the satellite exactly at the same place every second day to make repetitive observations with constant view angles, and a technological payload (IHET, Israeli Hall Effect Thruster) to change the satellite's orbit (that's why there is a blue and a red circle in VENµS's logo). It may sound a bit odd to couple two such missions on a single spacecraft, but anyway we found ways to accommodate them.
The current plans for Venµs Mission (VM) are as follows :
- VM1 : Venµs scientific mission is supposed to work until Mid 2020 at 720 km altitude, imaging 123 sites with a 2 days repeat cycle
- VM2 : Venµs altitude is progressively decreased to 410 km using the IHET engine
- VM3 : low altitude orbit keeping, compensating drag, while continuing to image as a secondary mission at 410 km (which is an orbit with a two days repeat cycle)
The interest of VM2 and VM3 is to show the capacity of the IHET to drastically change the orbit, and to compensate the atmospheric friction on the satellite at 410 km. At 410 km, the Venµs resolution will be close to 2,5m, but will require a rotation of the spacecraft for motion compensation. The viewing capacity of the satellite will therefore be reduced.
But the plans for VM2 and VM3 phases are principles which are going to be detailed and finalized this autumn during a Joint Steering Committee with France and Israel. It is therefore time to receive suggestions and ideas from the community of Venµs users.
We have already had our own ideas, such as :
- keeping Venµs Satellite on the current orbit for a longer time to allow for a longer scientific mission
- select the one day repeat cycle orbit at 560 km altitude instead of two days orbit at 410 km
- include observations from different viewing angles over a few sites to work on directional effects
But the more of us, the more imagination. Please feel free to rack your own minds and to suggest your ideas. Do you remember this experiment that you dreamed to be able to do with a high resolution optical satellite, a few months ago, but were never able to implement ? Maybe VENµS can do it... or maybe not, the only way is to ask us.
Feel free to add a comment here, or to send us an email, before mid August.
Philippe Gamet, Gérard Dedieu, Olivier Hagolle
|Observable zones during VM1 phase||Observable zones during VM3 phase... if we do not change the current project|