[X] My Assistant

[abalone]

Just 17 hrs and 8 hours from closest approach. Current view.

http://space.jpl.nasa.gov/


Last sim is with about 15 min to closest approach in about 7hr 45 min,

.....what a view!!!!!

Attached thumbnail(s)

 

[djellison]

You CAN go and get properly calibrated data...

BUT

The JPG's that get put in the Cassini and MER websites are automatically stretched, and there is no way of getting them back to any form of calibrated data.

As an experiment - take a calibrated MER or Cassini image - then in photoshop, do 'auto levels'. - that's basically what you're getting - and there's no way to reverse or backward engineer the process in any way whatsoever. Dont both trying, it's an impossibility. Sadly there are some people ( none here thank goodness ) who claim to make 'true' colour imagery from the JPG's. They're just kidding themselves.

The reason they do it is because of the huge range of brightness we get from image to image - they do it to be sure that we can actually see something every time - if they didnt, half the images would be too dark to see half probably too bright

Notice that they've not been flatfielded either - if you compare a raw JPG, and then find a calibrated one - it's like two different images. You can fudge it a bit - you can have a play - but you cant - you just cant get to anything like a calibrated image from the JPGs. It cant be done.


Doug

[helvick]

As an experiment - take a calibrated MER or Cassini image - then in photoshop, do 'auto levels'. - that's basically what you're getting - and there's no way to reverse or backward engineer the process in any way whatsoever. Dont both trying, it's an impossibility.  Sadly there are some people ( none here thank goodness ) who claim to make 'true' colour imagery from the JPG's. They're just kidding themselves.

Oh well. I knew that you couldn't make "true color" images from the files posted as is but I hadn't known that they were mangled by auto-levelling. I was going to try to build some code to try to calculate tau from the sun shots but that would be pointless if this is going on.

So the only way to get the original data is to wait until it's released to PDS or the MAN?

Grr.

[djellison]

So the only way to get the original data is to wait until it's released to PDS

Yes - and MER data gets released more frequently and with less of a delay than any other mission I know of. Up to sol 360 is available now, and up to Sol 450 will be available in two weeks time. If you tried to do Tau measurements from the JPG's - you'd end up with exactly the same value for both rovers for 600 sols

Doug