Venus Express Options

[tedstryk]

If all goes well, Venus Express will be a major topic for discussion in this forum a year from now. Does anyone know how good the surface coverage will be from VIRTIS and VMC? My understanding is that VIRTIS will obtain low resolution multispectral maps, and that VMC will, in addition to cloud monitoring, have one channel that can see the surface, but I don't know at what resolution or at what quality. It will be nice to have some non-radar images of Venus' surface besides the Venera snapshots and the shadowy images from Earth and Galileo's NIMS.

Ted

[dvandorn]

Your diagram shows the most common Hohmann transfer orbit, achieved by reducing the aphelion to coincide with the orbit of Venus (preferably when Venus itself is occupying that point along its own orbit).

There is another type of Hohmann trajectory for this type of mission. Instead of braking against the Earth's solar orbital velocity, the spacecraft thrusts at right angles to Earth's near-circular orbit (likely directly towards the Sun), creating a lopsided orbit with a perihelion at Venus and an aphelion well outside of Earth's orbit. The good thing is that the average orbital velocity of such an orbit is very nearly the same as the Earth's velocity, so you don't need to brake so much. The bad thing is that it takes even more energy to enter this transfer orbit, and your approach speed at Venus is somewhat higher, requiring more energy to brake you into orbit.

It gets you there a little faster than the brake-against-solar-orbit method, but it takes more energy.

-the other Doug