[X] My Assistant

[elakdawalla]

There is now PDS-format JunoCam cruise and Earth flyby data available; it's been submitted to the PDS, but MSSS has gone ahead and posted it on their website. I've created an index page to it here. Unlike my usual index pages, there aren't any thumbnails because of the odd nature of JunoCam images, with their long skinny shapes and interleaved framelets. I haven't played much with these data because it's a bit beyond my skill -- I look forward to seeing what any of you can do with it.

[Gerald]

In the meanwhile I've looked at all the 2x121 IMG files, only at few in more detail.

Filename convention with JNCE_2013282_00M103_V01 as an example:
- 3 letters "JNC" for JunoCam,
- 1 letter, "E" for EDR, "R" for RDR,
- "_" always,
- 4 digit year,
- 3 digit day of year,
- "_" always,
- "00" common in all files thus far,
- 1 letter for applied filters, "A": all, "C": colors red, green, blue, "R" red, "G" green, "B" blue, "M" methane,
- 3 digits image counter,
- "_V" version prefix always,
- 2 digits version number.

The IMG files are raw data without header. The header is instead in a separate LBL file.
EDRs are 8-bit unsigned char, RDRs 16-bit unsigned short, big endian encoded, hence need to be swapped for processors of Intel type.
Some of the "methane" test images use sampling factor 2, and are 816 pixels wide - that's a little less than 1648/2, starting with 2013107_00M053.

The RDR LBL files say

SAMPLE_BIT_MODE_ID = "SQROOT"

like the for the EDRs, but they look linearized to me at first glance.

Here a comparison of an 8-fold enlarged crop of EFB13 with the according files JNCE_2013282_00M103_V01, and JNCR_2013282_00M103_V01, the EDR converted in a straightforward way, the 16-bit RDR grey values divided by 20.25 to use the whole grey scale range:


There are at least two kinds of differences between EFB13 and the EDR:
- EFB13 - at least the version one I worked with - shows JPG artifacts,
- the EDR image shows 16x16-pixels macroblocks, possibly to account for HDR.
The macroblocks are present in the RDR, as well.

I didn't find information, how the raw data numbers can be restored.
So some questions about alternative approaches arose:
- Do there exist additional tables of grey value offsets for each macroblock?
- Does there exist a convention how to calculate the relative offset between two neighboring macroblocks?
- Is a subsequent application of a H.264-compliant or some similar deblocking post-process assumed?

After solving the macroblock question, some of the EFB images might eventually return better results than the initial EFB images.

Several images appear well-suited to study
- image geometry, effects of TDI, possible probe nutation, using stars,
- stray light of the Sun as a well-defined source of light.

[mcaplinger]

I didn't find information, how the raw data numbers can be restored.
So some questions about alternative approaches arose:
- Do there exist additional tables of grey value offsets for each macroblock?
- Does there exist a convention how to calculate the relative offset between two neighboring macroblocks?
- Is a subsequent application of a H.264-compliant or some similar deblocking post-process assumed?

I'm not sure exactly what you mean by this. The 16x16 block artifacts are from the onboard data compression (same as was used for the MOC way back when -- JPEG-like but with 16x16 transform blocks.) There is no way in general to restore anything as the raw image was never transmitted.

The only difference between the EDR and the RDR is that the RDR has been linearized and a radiometric scale factor applied.

If this had been a real PDS release you would also have access to the documentation. That release is coming but I don't know when; unlike previous missions we don't deliver directly to the PDS. For now I'll see if I can post the documentation on the web site.