MEX VMC - Back on, and online! Options

[djellison]

I heard about this 24 hours ago, and couldn't believe it - this is EXACTLY what has been missing from ESA. MASSIVE kudos to the ESOC MEX flight ops team for doing it

http://www.esa.int/SPECIALS/VMC/index.html

The last time I wrote a post and hit 'submit' at UMSF with a smile this big on my face, was when Oppy successfully got out of Purgatory.

[ormstont]

Well, part of the difficulty is that we have no way of predicting how bright Mars will be in a given location at a given phase angle. I'm sure one exists but our aim is always to allow the public to guide VMC activities - as I say, you are the operators of this instrument. If anyone comes up with a way of predicting it then I'd be more than happy to implement it!! I implemented the 4 step exposure setting as a workaround for this - guaranteeing whatever the observation we should get some well-exposed shots.

That's a good point about knowing the exposure settings - I'll see how we can work that into the routine flow of information and processing of each image. For a guideline though, the first image of every observation is always 14ms. For the rest of the observations I'd have to look for you on Monday at work, will do that and get back to you then.

For the flat field - I'm vaguely aware of what the term means - would it be a long exposure image with the spacecraft pointed at space? If you let me know roughly what I need to command MEX/VMC to do then I'll try and schedule a slot when we can do it. I know I use this as a mantra...but it's everyone's instrument, you let us know what to do!

[ugordan]

would it be a long exposure image with the spacecraft pointed at space?

That would be a dark frame, used for figuring out how the background signal increases with exposure (varies with temperature, hot pixels, etc). Part of wanting the exposure setting comes from the desire to have a rough model for dark background - two separate exposure images of a same target will produce different colors for different amounts of background signal. For example, a short exposure with VMS typically shifts overall colors towards blue as the background (grayish) overwhelms the Mars signal.

A flat-field is usually produced by imaging a sufficiently bland target so any noise in the image is variations in pixel sensitivity, crud in the optics, vignetting etc. This can be divided out from subsequent images to provide better S/N ratio. I don't expect we can get a look at a bland target now that we're at Mars, that sort of thing could have been done back on Earth, but then again this is not a scientific camera so most likely wasn't "calibrated" this way.

[Paolo Amoroso]

I don't expect we can get a look at a bland target now that we're at Mars, that sort of thing could have been done back on Earth, but then again this is not a scientific camera so most likely wasn't "calibrated" this way.

Would this Iris technique for extracting a flat field from science images, or something similar, be useful with VMC images?


Paolo Amoroso