The Planetary Society Blog
By Emily Lakdawalla
VEXAG meeting: Venus Express status
May. 1, 2006 | 20:45 PDT | May. 2 03:45 UTC
Next up after Larry Esposito was Adriana Ocampo, from NASA's Science Mission Directorate. (I should also note here that Adriana is on our Advisory Council). I don't have time tonight to summarize her talk but I want to quote here the shout-out she gave to ESA. "I wanted to start by asking Hâkan to stand up, to give congratulations for a successful VOI!!!!!!!!!" (The number of exclamation points there is a direct quote from her PowerPoint presentation.) There was much applause in the room; NASA may not be at Venus, but ESA sure is!
I'm going to skip directly to what Hâkan Svedhem had to say about Venus Express (and then I'm quitting for the night). When he stood up to talk, there was applause again from the room. "Venus Express is really doing fine and I am very happy that is the case. We have come to the point now where things really look good." He began by giving an overview of the instruments, which I'll skip since there's a page on this site on Venus Express' instruments.
He showed the shape of the science orbit, and here's a detail I hadn't noticed before. The orbit is a 24-hour orbit because that simplifies the planning of when Venus Express returns its data. All data from two hours before to two hours after Venus Express' closest approach is returned through ESA's dish in New Norcia. All the rest is returned through their other dish, at Cerberos. "It is all about lowering costs with ESA," Hâkan smiled.
"The capture orbit period was 3.5 hours longer than expected; this was a very good result. This enables all the science that was designed for the capture orbit. We had 6 slots in that orbit" for science observations, Hâkan reported, and all of them were accomplished. Furthermore, "the spacecraft has demonstrated a very strong robsustnness and is working well. There have been no safe modes at all so for (versus 20-plus for Mars Express)." Recall that Venus Express' design is based upon Mars Express. "We had problematic substytems on Mars Express, but these all operate well [on Venus Express]. The thermal design is performing just as it should; no problems."
He went on to an overview of the instrument status. "VMC operates okay, though there were some problems with flat field and calibration. These have now been improved. VIRTIS works very well in both modes. SPICAV works well in nadir mode; stellar and solar occultation modes and SOIR channel are still to be checked out. MAG is continuously operating, only solar wind so far." He explained that the magnetometer has two sensors, one internal to the spacecraft to detect the contribution of the fields from the spacecraft, and one on a one-meter boom; but the data from the one on the boom looks great even without the correction from the internal measurements. "ASPERA works well, but the data is not yet fully analyzed. And VeRA: the Ultrastable Oscillator is okay, but is still to be characterized after Venus Orbit Insertion for stability, drift, and noise."
There's only one instrument left, and it's the only one delivering bad news to Venus Express. "Then we have a little problem here with PFS," Hâkan explained. "In the launch configuration it has a mirror which is the one that directs the beam to the planet or to cold space or to internal blackbody source for calibration. The launch configuration is the black body pointing. After launch, the launch configuration checked out fine; less susceptible to noise from the spacecraft; everyone is happy. But when we tired to change to something other than black body, we got less happy." The mirror was frozen in its launch configuration. Since Venus Orbit Insertion, the situation has changed a tiny bit for the better, but it's definitely not fixed. "We have been checking up a little bit, because indications show it has moved a bit but not completely. It is not looking any more at the black body; it is at a position between the outside and the blackbody. There is still hope."
So, finally, Hâkan got to the data. He began with the two images that have already been published. "First VMC image was not too impressive; at this time we had not improved flat field. We were happy to get something down." He also showed the VIRTIS picture that they released earlier.
So then he showed some new data, not yet released, and I wish I could reproduce it here. It is GORGEOUS. There are beautiful feathery details in the clouds, and all kinds of subtle color variations. He showed shots from all six science observations, and highlighted the "polar dipole," an oblong feature that you can see in the clouds, rotating from one image to the next. It's sort of an oval shape, about twice as long as it is wide. It looks kind of like it has 2 lobes."
(I asked Kevin Baines later if these images were coming out in public release, and he said they probably wouldn't for a while; he said that they're really looking forward to the COSPAR meeting in Beijing in July, and that there will likely be a lot of public releases happening then.)
Finally, Hâkan showed a movie from the Venus Monitoring Camera from the pericenter approach. VMC has a circular field of view, so the movie is kind of like looking out a porthole as the spacecraft swings by; Venus' clouds totally fill the field of view. You see bands of dark and light clouds wandering by; there are very feathery boundaries between the bands -- like there is a horizontal striping, but someone has taken a feather and drawn it across at an angle of 30 degrees to the bands, feathering their edges. I asked Larry Esposito about this later and he said that they were really not sure what caused the feathering, that it likely had something to do with compositional variations among the clouds, and that they were very excited about trying to figure it out.
So that's it for tonight -- I'll have to put off writing about the rest of the meeting until tomorrow.
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