That little pole and an image file name decoder ring

First off, thank you Kano for such an excellent article on the complicated issue of color pictures on Mars. The least I can do is answer some of your questions.

The little silver pole is the low-gain antenna. It is used for low data rate communication, a few hundred bits per second, directly with Earth using X-band frequencies (around 8 GHz). It works over a wide range of angles, and so doesn't have to be pointed like the high-gain dish antenna. We use the low-gain antenna to send commands to the rover at low rates, around 30 bits per second, when the rover is awake but not using the high-gain to send data to us at the time. The low-gain is also a backup in case the high-gain pointing isn't working for some reason. We can work through the low-gain to fix it.

Now the secret decoder ring for the image file names. Taking one example file name from your article:

2P126644567ESF0200P2095L2M1.JPG

The breakdown is:

"2" for Spirit. "1" is Opportunity. (Don't ask.)

"P" is Pancam. Other choices are N - navcam, F - front hazcam, R - rear hazcam, M - microscopic imager, and E - EDL camera.

The next nine digits are the time the image was taken in seconds since noon UTC on January 1st, 2000.

The "ESF" is the product identifier, meaning a raw sub-framed image. There are many three-letter identifiers. Some common ones: EFF - raw full frame, FFL - full frame linearized, SFL - sub-frame linearized, EDN - downsampled raw image, DNL - linearized down-sampled, ETH - raw thumbnail, THN - thumbnail linearized (doesn't quite follow the convention). Linearized means that geometric optical distortions have been corrected. There are others for various levels of processing of the images.

"0200" is site 2 and position 0. We increment those counters when driving. Position is automatically incremented for each piece of a drive. We decide when we want to declare a new "site" to help distinguish the images.

"P2095" is the identifier of the command sequence that produced the image. This makes it easy, for example, for the person who wrote the sequence to find the images that were taken by their sequence.

"L" is the left eye. It can also be R - right, B - both, M - microscopic, or N - not an image.

"2" is the filter position, in the range 0..8 where 0 is no filter or not applicable.

"M" is the product creator, in this case the MIPL automatic image processing that is part of the MER downlink system. Other choices are A - Arizona State University, C - Cornell, F - USGS at Flagstaff, J - Johannes Gutenburg University, N - NASA Ames, P - Max Planck Institute, S - science operations team at JPL, U - University of Arizona, V - visualization team at JPL, or X - other.

"1" is the version identifier.

Dr. Mark Adler
Spirit Mission Manager

Ah Excellent, thankyou very much Dr. Adler for clearing that up. It is much appreciated.

One more clarification if I may, does spirit send back any data related to its auto exposure control when transmitting the images? If so is it available online anywhere?

Or is the Earthside image processing software able to recombine the images without that information?

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[Edited on 20-1-2004 by Kano]

Madler since you look like you work for NASA, are there any video or pics that were sent from the rover that are not online? If you do happen to have any, would you mind sending them to me please.

Also, thanks for the info madler.

Yes it does send back a bunch of information about the image, like the exposure time, camera pointing, temperature, etc. However as far as I know, that data is not available online. Once this data is archived in a few months, all of that data will be included and documented. All of the mission data will be available at the cost of duplication.

Mark Adler

Ah I see, thankyou once again Dr. Adler for taking the time to respond. It has been a great help in our understanding of the good work you and your team are doing.