Bright spot on Venus Options

[stevesliva]

For Cassini I remember there was a re-design after discovery of Enceladus' plumes by the magnetometer. There were 4 months in between the flybys and I think this was an 'all hands on deck' kind of moment.

From reading the Cassini status reports, the biggest rip-up is changing the trajectory, the second biggest is changing the pointing, and the third biggest is changing the timing. For timing updates, they have whitespace in their plans, for pointing updates they obviously have to throw out the old and begin anew, but they can do this with reasonable speed given proper motivation. A few weeks, I think?? But that is a special request.

[ugordan]

for pointing updates they obviously have to throw out the old and begin anew, but they can do this with reasonable speed given proper motivation. A few weeks, I think?? But that is a special request.

I think it would take several weeks at least. New sequences are uploaded onto the s/c weeks ahead of execution and they would need to be worked out and tested and validated on the ground before that.

[john_s]

The July 2005 Cassini Enceladus flyby was definitely a special case. The decision to change the trajectory to reduce the close approach distance was made in mid-April 2005, just 3 months before the encounter. There was already a fully-developed observation plan, but we only had to tweak the period around close approach (maybe +/- 30 minutes or something like that). It was a scramble, but of course it paid off big time. I don't think we've made a tweak of that magnitude at such short notice since then- usually even the detailed observation sequence is pretty much frozen 4 or 5 months out. I suspect that if there was a big impact on Saturn, say, something could be done to observe it with a lead time of a couple of weeks, but it would be a major effort that would take away from other high-priority planning work- not a decision to be made lightly.

You can be a lot more flexible in planning observations for a spacecraft that can happily sit tight while you figure out your next move, than for a spacecraft that's careening through the solar system at many kilometers per second!

John

[stevesliva]

I think it would take several weeks at least. New sequences are uploaded onto the s/c weeks ahead of execution and they would need to be worked out and tested and validated on the ground before that.

Yeah. And they need to hold the meetings where they tell the instrument teams on the wrong side of the spacecraft that their science is getting removed.

[cndwrld]

Ummm... let me get this straight. VEX ops are pre-planned four months in advance and nothing can be changed in those pre-planned ops plans? So that any follow-up on transient phenomena literally cannot take place for at least four months?

If that's the case, then we truly don't have a resource at Venus that can do anything at any given time except its pre-planned program, which will always be a good four months out of date. I guess we can take "respond to transient phenomena or rapid changes in environment" off the list of VEX's abilities. (I know, it's never been a claim of the project.... but, as Doug says, the whole thing gives me rage.)

But, to be fair... with what do I compare this? Can Cassini's op executions be changed after they are loaded into the spacecraft? If so, how quickly? How fast can Cassini respond to some changing circumstance? How about Hubble? We know Hubble had been packed solid with use requests and that it was still capable of being re-tasked to get Jupiter images within a week of the first detection of the impact on old Jove.

Maybe we're all just too used to ops plans like those for the MERs, where what we do tomorrow is highly impacted by what happened today. Obviously, many NASA probes (especially those in the outer system) don't have that kind of operational flexibility, either. So... how does VEX compare to other planetary probes in terms of being re-tasked?

-the other Doug

Any other questions?

[tedstryk]

With the slow Venusian rotation, if the white spot is caused by something ongoing on the surface and is superrotating with the atmosphere, wouldn't it become a white band?

[Phil Stooke]

Good point. It would have to be one gigantic belch (if I can use that vulgar expression here) that rose into the upper atmosphere and rotated with it.

In the interests of science, I am now going to practice my belching. Results will not be posted.

Phil

[tedstryk]

We need to check the satellite maps. If a big, white cloud has formed over southern Ontario, then maybe the events are similar.