Cassini image database & updates, And notifications of PDS data releases Options

[Bjorn Jonsson]

I have noticed that the January 1, 2007 Cassini PDS release is already available, see http://pds-imaging.jpl.nasa.gov/data/cassi...assini_orbiter/

I haven't downloaded all of the imaging data and I'm just beginning to digest what I already have but there are some beautiful images of Enceladus' plumes and satellite mutual events, images of the G and D rings and interesting images of Saturn's nightside and fairly good Iapetus images.

Radar and VIMS is also available.

All in all a nice 'Christmas gift' .

[Decepticon]

and fairly good Iapetus images.

Radar and VIMS is also available.

Would love to see this!

[volcanopele]

This release covers the time period from January 1 to March 31, 2006. No RADAR SAR swaths were taken during this period of time. There were three Titan flybys: T10 (ORS covering anti-Saturnian hemisphere), T11 (ORS low-phase inbound over sub-Saturnian hemisphere), and T12 (ORS moderate phase over anti-Saturnian hemisphere). T11 has some good observations, never messed with T10 or T12 too much since it covered the same territory we had seen over and over again without adding to much new information.

Beyond Titan, there is a decent sequence at Enceladus from Rev20 (look for images in the N1516153055 through N1516171418 range). There are also decent Rhea observations during each orbit (Rev20-21-22). rev22 has some decent Rhea saturn-shine images. Finally, Rev21 has a couple of observations of Tethys over Penelope crater.

EDIT: actually, there was a distant SAR look on T12. I'll try to post that within an hour.

EDIT again...: and that isn't available yet. Hopefully it will be up by Monday.

[ugordan]

Here's an 8 frame animation showing the late January 2006 "flyby" of Iapetus from this PDS batch. Closest approach was around 880 000 km.


Three of the frames are natural color RGB composites, the rest are stretched color IR/G/UV processed to match natural color views. Images have been magnified 2x for better visibility.

[remcook]

cool

[TritonAntares]

Here's an 8 frame animation showing the late January 2006 "flyby" of Iapetus from this PDS batch.
Closest approach was around 880 000 km.

Three of the frames are natural color RGB composites, the rest are stretched color IR/G/UV processed to match natural color views.
Images have been magnified 2x for better visibility.

Nice animation...

More on Japetus there? What about the november 27th far-encounter in ~2 mio. km distance?

Bye.

[Michael Capobian...]

Here's an 8 frame animation showing the late January 2006 "flyby" of Iapetus from this PDS batch. Closest approach was around 880 000 km.

Wow. That's a really good way to tie the Moat/Snowman region to eastern Cassini Regio. That's the first time I've noticed the large crater on the eastern edge of the Landslide Basin. And it's interesting that the claw marks are parallel to the tic-tac-toe ridges. (It really would be nice to have some official names for these features. )

Michael

[ugordan]

What about the november 27th far-encounter in ~2 mio. km distance?

November 2006? That won't hit PDS for another 9 or so months. By then the closest flyby ever will be over!

[elakdawalla]

EDIT: actually, there was a distant SAR look on T12. I'll try to post that within an hour.

EDIT again...: and that isn't available yet. Hopefully it will be up by Monday.

Jason, is that T12 SAR up yet?

--Emily

[volcanopele]

Not that I can see. It is possible that I was wrong and that there wasn't a distant SAR look on T12, but I could have swore they did.

[JTN]

(pointed here by Emily's post in another thread)

It is possible that I was wrong and that there wasn't a distant SAR look on T12, but I could have swore they did.

FWIW, the mission description only mentions radiometry/scatterometry (the obs mentioned in the data playback section are RADAR_022OT_WARM4TI12001_RIDER and RADAR_022TI_T12OUTRAD001_PRIME). I also found T12_SEQ_DESIGN_MEMO.PDF, which says:

Like T4, this RADAR data collection includes only radiometry and scatterometry. RADAR will not operate at the closest approach time, therefore no altimeter or SAR data can be collected. The radiometry scans will include compressed scatterometry for the second time. Before the two outbound radiometry/compressed scatterometry scans, there will be a small scatterometry segment that follows an iso-doppler SAR-style profile with a constant incidence angle of 20 degrees.

[Bjorn Jonsson]

The April 1, 2007 PDS release is out with new ISS, VIMS and RADAR data.

I have looked at all of the ISS images and updated my summary of Cassini images at http://www.mmedia.is/bjj/misc/css_stuff/im...s_overview.html.

I will soon be adding a list of flybys for each satellite near the top of the document ("a summary of the summary").

The ISS release wasn't particularly interesting to me this time. Some highlights:

* Images of Iapetus down to a range of ~600,000 km
* Two targeted flybys of Titan
* Many spectacular satellite mutual events since Cassini was very close to the ring plane
* Interesting images of Hyperion, Janus, Atlas and Pan
* Rhea global color at a range of ~480,000 km
* Many distant high phase images showing Enceladus' plumes
* Saturn star occultations

Incidentally, I ran into a few cases of erroneously formatted numbers in several of the index.tab files that caused some problems when loading these files into an Access database so I'm going 'complain' to the PDS. Example: 1.0524616e-
I suspect 'very small' numbers may get incorrectly formatted, possibly numbers smaller than 0.001 or 0.0001.

I could make the database available if someone can host it, it's too big for me to do so (about 55 MB zipped). It contains all of the information from all of the index.tab files on volumes COISS_1001 to COISS_1009 and COISS_2001-COISS_2023.

[ugordan]

Is anyone having luck accessing the PDS site, namely http://pds-imaging.jpl.nasa.gov/? It's broken for me at least since yesterday.

[tedstryk]

Is anyone having luck accessing the PDS site, namely http://pds-imaging.jpl.nasa.gov/? It's broken for me at least since yesterday.

No, no luck for me.

[Bjorn Jonsson]

Same thing here. Fortunately I finished downloading the ISS data before this started .

[volcanopele]

http://pds-imaging.jpl.nasa.gov/data/cassi...assini_orbiter/ works fine for me right now.

[volcanopele]

Some highlights from my perspective are the T13 radar SAR swath (the one that crosses Xanadu) and the distant encounters with Janus and Pan.

[ugordan]

Here's Janus, an approximately natural color view and enhanced stretched color to bring out subtle color differences:

Unlike Telesto which appears bluish in natural color and very faintly orangish in stretched color, Janus is more like other rocky moons -- Prometheus and Pandora. Magnified 2x.

[elakdawalla]

I could make the database available if someone can host it, it's too big for me to do so (about 55 MB zipped). It contains all of the information from all of the index.tab files on volumes COISS_1001 to COISS_1009 and COISS_2001-COISS_2023.

After a bit of a tussle with the remote server I've managed to upload the file, so it's now hosted at:
http://filicio.us/tpss3/files/17314/cassini_images.zip

It's 55 MB and unzips to a 500-MB database. I'll let Bjorn chime in with any comments he'd like to make about it. For my part, I'll just thank Bjorn for assembing this whole thing -- and beg for the inclusion of the north_azimuth field that you calculated for some Saturn images for all the images in the next version of this database.

--Emily

[Bjorn Jonsson]

A few comments:

This is a Microsoft Access database containing two tables, coiss and coiss_revised. Coiss simply combines all of the index.tab files on the Cassini ISS volumes 1001-1009 and 2001-2023 into a single database without any significant modifications, except for the rejection of erroneously formatted numbers (see the list of errors at the end of this message).

The coiss_revised table contains updated values for a few fields. These values are *probably* slightly more accurate (from my experience when doing a cylindrical map of Saturn) than the original values although I cannot completely guarantee this. They are computed from the latest SPICE kernels (CK and SPK). The NORTH_AZIMUTH value is also included as there's no equivalent field in the coiss table. At this time only a few images are included in coiss_revised. I don't know the exact geometric meaning of north_azimuth_clock_angle in the index.tab files but it is totally different from north_azimuth so I added north_azimuth in a separate table. However, I have only determined it for a few images (70 - mostly the ones I used to do a map of Saturn) but plan to do so for all of the images, possibly before the next batch of images gets released 3 months from now.

There are a few simple queries there as well that I decided to include as a simple example of what can be done.

I use this database extensively when searching for interesting and/or specific images, both from within Access and directly from programs I have written. I rarely use the PDS to search for images, I mainly use it to download entire data volumes.

As previously mentioned I found errors in some of the index.tab files. The errors I know of are:

coiss_2017: There are erroneously formatted floating point numbers in rows 1253-1257 in index.tab, columns 2541-2551 (SUB_SPACECRAFT_LATITUDE). I tried 'guessing' the correct values. These are images N1512191594_1.IMG, N1512191728_1.IMG, W1512191728_1.IMG, N1512191860_1.IMG and N1512191993_1.IMG.

coiss_2020: There are erroneously formatted floating point numbers in rows 170-171 in index.tab, columns 2628-2638 (TARGET_SOUTHERNMOST_LATITUDE). I fixed this manually - the fixed values are a guess and the correct value to use is uncertain. These are images N1517273822_1.IMG and N1517273855_1.IMG.

coiss_2021: There are erroneously formatted floating point numbers in rows 1980-1990 and 2648-2649 in index.tab, columns 2541-2551 (SUB_SPACECRAFT_LATITUDE). I fixed this manually - the fixed values are a guess and the correct value to use is uncertain. These are images W1520869299_1.IMG, N1520869388_1.IMG, W1520869388_1.IMG, N1520869616_1.IMG, W1520869616_1.IMG, N1520869705_1.IMG, W1520869705_1.IMG, N1520869934_1.IMG, W1520869934_1.IMG, N1520870023_6.IMG, W1520870023_1.IMG, W1521409807_1.IMG and N1521409944_1.IMG.

coiss_2023: There are erroneously formatted floating point numbers in rows 2785-2788 in index.tab, columns 2616-2626 (TARGET_NORTHERNMOST_LATITUDE). As previously I fixed this by trying to guess the correct values. These are images N1530372696_1.IMG, N1530372841_1.IMG, N1530372986_1.IMG and N1530373131_1.IMG.

There might be more errors.

[tallbear]

Is there any sort of search capability in existence for any of the PDS ISS released products ??

For instance... if one wanted to look for NAC images where the boresite intersect was in the B-ring
and the range was under say 10 Rs ??? or where the target was PROMETHEUS and the range was under
1M km ??

my first impression is that the INDEX.TAB files *seem* to have some problems ... but perhaps I've not
gone thru enough documentation .... any pointers on documentation source would also be great !!

Thanks !!

[elakdawalla]

I'd say the best thing to use to search would be Bjorn's database, referenced earlier in this thread. He's already got basic queries on some targets with ranges in there -- they'd be easy enough to modify to get your Prometheus-under-1Mkm search, but I don't know how you'll do the B-ring one.

Bjorn, if you update your database with the tables of info from the latest release I'll gladly host it for you.

--Emily

[Bjorn Jonsson]

What tallbear wants to do should be trivial to do in my database, in fact the reason I made the database was that I wanted flexible search capabilities. The Prometheus-related query is trivial (there are similar sample queries I did in the database where the target is different but they illustrate how to do this).

The B ring query is probably easy as well although I should mention that I have not tried something like it (I'm on my laptop at the moment and the database is on my desktop computer so I cannot try it at the moment).

I didn't notice any problems with the INDEX.TAB files except for the ones mentioned in my April 3 message earlier in this thread. The database contains all of the fields/columns from all of the index files.

Bjorn, if you update your database with the tables of info from the latest release I'll gladly host it for you.

Great! I will be updating the database in early July following the July 1 PDS release. The updates can be imported into the database so I do not have to upload the database again in its entireity when I update it.

[tallbear]

Cool... I'll try Bjorn's database....read over what it takes to get it up and running....
It's interesting that the Rings Node has really neat search capabilities for Voyager
images... but for Cassini ... it's unmannedspaceflight.com that's forging the way ....
...Thanks ... Great Work ... I'll get in and start nosing around...

[Bjorn Jonsson]

The July 1, 2007 PDS Cassini release is starting to appear. The ISS and VIMS stuff is already there:

http://pds-imaging.jpl.nasa.gov/data/cassi...assini_orbiter/

So far I have downloaded only about 1500 ISS images and have looked at only a few of them but there's one particularly interesting imaging sequence in this release: The ISS data includes the famous imaging sequence showing Saturn and the rings backlit with the Earth visible as a tiny bright spot. That particular imaging sequence starts in directory data/1536725883_1537013377 on the coiss_2025 volume.

[elakdawalla]

Cool!

I've been wanting to do something to make PDS Cassini images easier to find but this data set is way too big for me to do a complete treatment on it. Instead, I was thinking of producing an index page to all moon images where the moon spans more than N pixels. The thing is I haven't decided what N should be yet. 200? 100? 128? What's a good number? I'd probably use a different number for the major icy sats than for the ringmoons and Lagrange point moons. Any thoughts?

--Emily

[scalbers]

Emily,

That would be pretty neat to see an index. From my perspective it sounds like you have some good numbers in mind. In the case for some of my maps I've used images getting down to just over 100-120 pixels, though most are over 200.

[djellison]

What would the diameter be for the middle of the disc to be 1 degree of latitude / pixel. That might be an appropriate figure to work from. My brain can't do the trig to figure it out

Doug

[scalbers]

Maybe 115 pixels?

[ugordan]

Yeah, it could be 115. 1/sin(0.5 deg).

[elakdawalla]

I sketched my little diagrams and chanted "SOH CAH TOA" and worked it out and yes it came to 114.6 pixels. That sounds like a good plan. I'll put in >114.

I ran that in to Bjorn's database as of March and got the following numbers of images:
Mimas: 422
Enceladus: 623
Tethys: 749
Dione: 884
Rhea: 1584
Hyperion: 677
Iapetus: 2181
Phoebe: 383

These numbers are a little on the highish side...running it down to 200 pixels across, here's what I get:
Mimas: 327
Enceladus: 603
Tethys: 308
Dione: 600
Rhea: 1150
Hyperion: 496
Iapetus: 1061
Phoebe: 227

(Interesting how much of a hit Iapetus and Tethys take, while Enceladus is virtually unchanged!)

...and remember that that's less than 2/3 of the way through the mission. I'm kind of inclined to go with the higher number so as not to have mind-numbing quantities of images where the moons aren't very big, but if someone makes the case that I'll miss out on too many phase angles or mutual events I'll try it with the lower-res ones included.

I should also add that I'm not real excited about downloading 25 volumes and will be more excited about doing this if I can figure out how to use Bjorn's database to write batch files for wget that will only retrieve the files I want...we'll see!

--Emily

[djellison]

Screw it - go for 2 pixels / degree 230 pixels for cash.

Doug

[Bjorn Jonsson]

I think it might be a good idea to limit this by resolution and not pixel size. A 115 (or 200) pixel diameter image of Mimas or Enceladus is usually much more interesting than a 115 pixel diameter image of Rhea unless you are interested in photometry. Another way of putting this: Make the size limit in pixels a function of satellite radius.

[elakdawalla]

That's not a bad idea. Got any specific recommendations?

--Emily

[David]

Hm, taking Mimas as your 114 px baseline, that comes out to:

Mimas 114
Enceladus 140
Tethys 292
Dione 306
Rhea 417
Titan 1405
Iapetus 392

Assuming I'm not working with ridiculously antiquated figures here...

[Bjorn Jonsson]

I now have the information on the just released Cassini images ready for getting added to the Access image database discussed earlier in this thread. That database includes everything up to and including the April 1, 2007 release. The files below add the images released on July 1, 2007.

Transferring the entire database file is an overkill so I prepared two Excel (!) files that can be imported into the database. The files are fairly small (less than 3 MB each). Emily has hosted them on the same server as the database:

http://filicio.us/tpss3/files/23158/cassin...es_index_24.zip
http://filicio.us/tpss3/files/23159/cassin...es_index_25.zip

In Access, do File -> Get External Data -> Import

What follows should be obvious, accept the defaults and when asked "Where would you like to store your data?" choose the table "coiss" in the list that appears next to "In an Existing Table:".

Thanks to Emily for hosting this together with the database.

[ugordan]

A little comparison of Cassini's solar eclipse as seen by VIMS and ISS:

The leftmost image is a gamma-correct (2.2 gamma) mosaic of four VIMS cubes and is probably closest to what the human eye would see. The middle image is additionally brightened and saturation increased. The rightmost image is a crop from the famous CICLOPS mosaic. Neglecting massive VIMS noise in the visual channel, if you increase the saturation the CICLOPS and VIMS colors appear pretty similar.

[ugordan]

Two short time-lapse sequences:

Three frames on the left show the opposition surge on part of the rings. Don't know which part though, probably A or B rings. The surge appears elongated probably because as VIMS was scanning the cube the opposition highlight moved. Also note ring darkening as phase increases.

The 5 frame sequence on the right was taken on 2006-08-18 and spans an hour and a half. Each VIMS scan took more than 10 minutes to read out. Noisy as hell. I removed most of the linear noise but it wasn't perfect and left some residuals as well as cosmic noise hits.

[scalbers]

Hm, taking Mimas as your 114 px baseline, that comes out to:

Mimas 114
Enceladus 140
Tethys 292
Dione 306
Rhea 417
Titan 1405
Iapetus 392

Assuming I'm not working with ridiculously antiquated figures here...

In addition to size, I think the relative abundance of available images could be a consideration. In this light, it's good for Rhea to have a larger number as there are quite a few hi-res images available. On the other hand, Iapetus has a relative scarcity of images so I would go lower - back to the 100-200 pixel range.

Titan makes sense to have a large threshold, partly as large images are needed to compensate for atmospheric blurring.

[elakdawalla]

I'm returning to this project after a hiatus. I am now trying to figure out what information will be valuable to include in the browse pages. There is a huge number of fields available in the database. Here is what I am thinking about including; let me know if there are any fields I've missed that you can't live without.

FILE_NAME (e.g. W1481738172_2.IMG)
TARGET_NAME (e.g. DIONE)
TARGET_LIST (listed only if it is not "N/A" or identical to TARGET_NAME -- picks up other bodies that may be in frame, useful for mutual events)
OBSERVATION_ID (e.g. ISS_00BDI_GLOCOL001_PRIME) <-- note you get information on which rev you're on in this one
IMAGE_MID_TIME and IMAGE_MID_TIME_SEC_FRAC (e.g. 12/14/2004 5:30:21.716) -- is this OK or is START_TIME better?
PIXEL_SCALE (e.g. 9.3249958) <-- in km
TARGET_DISTANCE (e.g. 156875.92) <-- in km. this is redundant with the pixel scale but I think it's useful to show both.
PHASE_ANGLE (e.g. 34.258215) <-- in degrees
SUB_SPACECRAFT_LATITUDE and SUB_SPACECRAFT_LONGITUDE (e.g. 11.092879 and 207.90797) <-- I prefer this to the CENTER_LAT and CENTER_LON because I think it makes more sense for images where the entire body is contained somewhere within the FOV.
EXPOSURE_DURATION (e.g. 5600) <--need to state units
INSTRUMENT_MODE_ID (listed only if it's been 2x2 or 4x4 binned, "SUM2" or "SUM4")
INST_CMPRS_TYPE (LOSSY or LOSSLESS)

Some questions:
Can I get away with skipping INSTRUMENT_ID? Whether it's WA or NA will be clear from the file name.
Are EMISSION_ANGLE and INCIDENCE_ANGLE important, or is there enough information contained in PHASE_ANGLE?

--Emily

[volcanopele]

Instrument_ID isn't important if you are listing both WACs and NACs, and the file name is listed. That field is just useful as a search criteria, e.g. you want to retrieve NACs only.

Emission angle and incidence angle is important if the object more than fills the frame. Emission angle is important if you are looking for useful Titan images.

[elakdawalla]

I just went through the process of creating an index page for Dione, using the 2 pixels per degree (=228 pixel diameter) size cutoff:
http://planetary.org/data/cassini/dioneattempt/
WARNING: to view this page requires you to download about 42 MB of data.
[Note: I didn't bother uploading the full-size images, only the thumbnails, so the images won't link to anything. Also, I didn't yet include all the fields I mentioned in my previous post; I did intend to include the filters and stupidly forgot. Next time around they'll be in there.]

This included more than 500 images, but after seeing the results I don't think it was enough. Cassini has so danged many filters that those 500 images were for a relatively small number of distinct observations (22), most of them on nontargeted flybys; the query did not pull in nearly as many global shots of the moon as I was hoping to get. So I think I will back away and try the 1 pixel per degree cutoff next time.

What do you think of the layout, with one observation per line? I think I will reduce the size of the thumbnails next time. They are currently 256 pixels -- I think I will reduce to 128 or even 100.

I used IMG2PNG to convert these, and did calibration, but the calibration didn't seem to work for the WAC images for some reason.

Comments?

Emily

[ugordan]

Wow, this is quite an undertaking you're doing there, Emily! You sure your server is good for all this data?

One parameter that might be nice to add is which way north is (IIRC can be approximated from from the so-called TWIST_ANGLE). I'd use IMAGE_MID_TIME as I think it's more reliable than START_TIME.

What do you mean by WAC calibration not working? 128 pixel thumbs seem about right, anything smaller might make more distant observations look bad.

[Bjorn Jonsson]

There are a few more fields I'd include, in approximate order of priority:

FILTER_NAME_1
FILTER_NAME_2
SUB_SOLAR_LATITUDE
SUB_SOLAR_LONGITUDE
INST_CMPRS_RATIO
DECLINATION
TWIST_ANGLE
RIGHT_ASCENSION

The first five are essential in my opinion. Possibly include VOLUME_ID and some of the RINGS_ fields as well.

Note: I'm using the field names from the Access database, not the fields in the INDEX.LBL files (which describe the contents of the INDEX.TAB files from which the database was generated). The field names are usually identical but there are a few exceptions where I broke a field from INDEX.LBL up into two fields, for example the two FILTER_NAME fields (because it seemed more convenient) and the SEC_FRAC fields (because as far as I know the maximum precision of Access dates is one second).

I'd use IMAGE_MID_TIME as you did rather than IMAGE_START_TIME.

The page layout looks fine but it contains a lot of stuff (42 MB) so maybe it should be broken up into several pages, probably by OBSERVATION_ID.

I'll see if I can find out why calibration didn't work for the WA images (it does on my machine when I use my big program from which IMG2PNG was cannibalized).

[tedstryk]

I like it. Perhaps you could do it with more images, but do it yearly (in other words, separate pages for 2004, 2005, 2006, etc). One thing (not sure if it is just because you are still working), the links to the PNG images don't work.

[ugordan]

I've stumbled upon an error in the latest batch, there are two polarized UV NAC frames, N1536539385_1.IMG and N1536539427_1.IMG incorrectly labeled as:

TARGET_DESC = "Tethys"
TARGET_LIST = "N/A"
TARGET_NAME = "TETHYS"
OBSERVATION_ID = "ISS_028TE_TETHYSORS001_CIRS"

When in fact they target Enceladus:



IIRC, I've also stumbled upon this incorrectly labeled sequence when browsing VIMS cubes. There in fact was a Tethys ORS sequence running just at about that time - 2006-09-09 23:51:20.0, could this be a case of a quick-n-dirty retargeting to get a couple of Enceladus shots without a dedicated observation?

[elakdawalla]

I've reduced the thumbnails to 128 pix and converted them from 16-bit PNG to JPG, and together that brings the page down to 2 MB of data, which is much better!

One thing that bothers me about this page is that there's a lot of redundancy -- it doesn't seem necessary to show thumbnails of all of the images of the same spot taken through different filters. I'm going to do some fiddling and see if I can come up with a different way to present this that has less redundancy, but shows more of the metadata.

Hmmm...

--Emily

[pat]

I've stumbled upon an error in the latest batch, there are two polarized UV NAC frames, N1536539385_1.IMG and N1536539427_1.IMG incorrectly labeled as:

TARGET_DESC = "Tethys"
TARGET_LIST = "N/A"
TARGET_NAME = "TETHYS"
OBSERVATION_ID = "ISS_028TE_TETHYSORS001_CIRS"

When in fact they target Enceladus:



IIRC, I've also stumbled upon this incorrectly labeled sequence when browsing VIMS cubes. There in fact was a Tethys ORS sequence running just at about that time - 2006-09-09 23:51:20.0, could this be a case of a quick-n-dirty retargeting to get a couple of Enceladus shots without a dedicated observation?

Yep, thats down to an error by the person who built the camera command for this observation. The observation, ISS_028TE_TETHYSORS001_CIRS, starts off by turning to Tethys and then tracking Tethys. At the end of the observation Cassini turns from Tethys to Enceladus and ends pointing at Enceladus ready for the next observation to take over. No observations of Enceladus were planned. Margin has to be added to turns to allow for uncertainties so Cassini probably spent 2 mins or so actually pointing at Enceladus right at the end of the observation.

An error was clearly made in syncing the camera command with the spacecraft pointing. When that particular camera command was excecuted the spacecraft was tracking Tethys, thats why 'TETHYS' is the value of the TARGET_NAME keyword. 'Tethys' is the value of the TARGET_DESC keyword becasue thats the photometric model that was used to calculate the exposures for the camera command. The camera command ran 'too long' and images of empty space were taken while Cassini was turning from Tethys to Enceladus, the 12 images from N1536538981_1.IMG to N1536539343_1.IMG. The final two images in the observation were shuttered in that final 2 mins or so of turn margin time when Cassini, or at least the ORS instruments, were pointed at Enceladus. Interestingly the first image taken during the slew, N1536538981_1.IMG is not of empty space but Tethys -- however Tethys is smeared indicating that Cassini must have started turning during the 1.2 seconds that the shutter was open while this image was being taken.

Actually on reflection this can also be explained by the CIRS team changing the spacecraft pointing design after the ISS (and VIMS) Teams had built the camera commands for their rider observations, possibily because the observation had to be shortened.

[ugordan]

Ahh, that explains it. Thanks a lot, pat, I'm always interested in learning in more detail how all these sequences are actually developed and executed at the low level. The shortening of the observation does seem like the most plausible reason. I did notice the one smeared image you mention, but the empty ones must have slipped me as "non-interesting".

Speaking of slew maneuvers, one thing I was always wondering is how much buffer time the cameras use when making mosaics of targets spanning over 1 FOV? Is it a couple of minutes or shorter? How fast can Cassini actually turn around say 180 degrees and steady up at the target pointing?

[elakdawalla]

OK, I've had a slightly different go at it.

http://planetary.org/data/cassini/dioneattempt/index2.html
This is a much improved 726k to download. Note that the links to full-size images still do NOT work.

I used the 1 pix/degree cutoff this time (923 images) and incorporated more metadata, but am only showing one image from each multispectral set. I think I am happy with the number of observations included now -- I think it's more like 44 -- but am not totally happy with the page layout yet. I was hoping to come up with something where I could almost fully automate the generation of the html, but the step of deleting redundant images (something that's really necessary to reduce the amount of data on the browse page) has to be done by hand, and that's time consuming.

Two things I forgot and will include in any future version: I wanted to put the file names in with the metadata, but they're not there (though they are preserved in the URLs, so at least you can see them that way); and I wanted to include the TARGET_LIST field at the end.

EDIT: I added one more thing -- I was curious to see how many of these observations had resulted in products released to Photojournal. Many have, but many have not; and there are also a great many Photojournal releases of images where Dione was smaller than my size cutoff (though many of these were multiple-body images, so the small size made sense). Notes on Photojournal releases are now on the page. Also, the look through Photojournal made me realize that I missed all the opnavs, because these have a target of "SKY" -- I need to modify my query to add in those opnavs. There were 20 or so that were within the size range.

I'm going to start uploading the full-size images now and leave it running overnight -- it's 800 Megs of data!! That's a bit more than I bargained for. Too many 16-bit images.

Comments?

--Emily

[pat]

Speaking of slew maneuvers, one thing I was always wondering is how much buffer time the cameras use when making mosaics of targets spanning over 1 FOV? Is it a couple of minutes or shorter? How fast can Cassini actually turn around say 180 degrees and steady up at the target pointing?

I'm not sure about the margin for turns while mosaicing but for a 180 degree slew the times are

Roll about X-axis ~30.5 minutes
Roll about Y-axis ~25.8 minutes
Roll about Z-axis ~16.4 minutes

using high power for the reaction wheels
and

Roll about X-axis ~58 minutes
Roll about Y-axis ~42 minutes
Roll about Z-axis ~38 minutes

using low power for the reaction wheels

and a 180 degree RCS turn is about 11 minutes

The settling time after a turn is nominally about 60 seconds I think.

[ugordan]

Wow, I assumed the reaction wheel figures were high but these are quite substantial indeed. Is the time difference primarily due to different mass distribution along each axis? I can't seem to dig up a schematic showing the orientation of principal axes, but this would suggest the Z axis running along the length of the s/c, parallel with HGA boresight and the X axis being the most inert of them, orthogonal to the plane in which HGA boresight and magnetometer boom lie?

How do these figures change with propellant depletion (if at all)? Optimizing slew maneuvers is no doubt one of the (many) factors in increasing useful observation times...

[ugordan]

I'm going to start uploading the full-size images now and leave it running overnight -- it's 800 Megs of data!! That's a bit more than I bargained for. Too many 16-bit images.

Comments?

I really like the new layout, much more bandwidth friendly and the color-coded filters are also a nice touch. How did you find all those Photojournal releases derived from Dione sequences - manually by dates?

One thing regarding the full size PNGs. They are 16 bit, but are very dark, perhaps a uniform scaling factor could be applied to all images to maximize DN in the PNGs. IIRC Bjorn's IMG2PNG does implement this feature. This would ideally be the highest scaling factor that keeps the brightest albedo object in the Saturnian system (i.e. Enceladus) from being overexposed, of course taking into account its weird zero-phase geometric albedo of 1.375. I don't know what scaling factor you currently use, but if low enough it might in fact reduce s/n ratio if the 12bit images are fit into 8 bit values.

[elakdawalla]

Thanks. For the Photojournal images, I just searched on Dione, and then I matched the dates and, when date was ambiguous (or, in one case, incorrect), I matched the phase angles and distances. A bit tedious but that's one thing I've been very curious about -- just how many of the "good" images have been released to the public in one way or another? It's not a bad proportion, it turns out, but it's not all of them by any means, and there is a LOT that can be done that hasn't yet been done with color data.

The 16-bit images do have a variety of brightnesses, but I did use IMG2PNG with the "-r" switch and all the Cassini calibration data to calibrate them as I did the format conversion. Clear and green filter images do seem to be pretty reasonable in their brightness, UV ones are pretty dark -- which is more or less what I expect, actually. Remember that Dione is somewhat dark as icy satellites go. Maybe Bjorn can comment on whether the full-size images look like they are supposed to, especially in the UV. I did get errors on every WAC image upon conversion though, so I'm not sure that those are properly calibrated. Of the 900 or so NAC images, IMG2PNG reported errors during the calibration step for about 20 of them.

On the next go-round I'll do Enceladus and we can see how different those look.

--Emily

[ugordan]

I was intrigued by some fairly big brightness differences between different filters in Emily's page. For example the UV images turn out much darker than when I throw them through my software. I decided to do a comparison of narrow angle frames N1507738546_2 (RED,CL2), N1507738663_2 (CL1,GRN) and N1507738491_2 (BL1,CL2). Below are simple RGB composites, modified only to resize and register the three filters:


The left image uses IMG2PNG converted data, the right one is my calibration result.

I didn't touch the channel balance in the left case, there are a couple of notes about my results:
I do all the calibration steps except dark current removal. In practice this doesn't amount to anything than a slightly brighter background signal in the longer exposed images (blue and especially UV in NAC and violet in WAC case) and is in no way capable of such a drastic difference. If you really kick up the saturation in my image, you'll see the bluish hue likely due to dark current.
Other than that, I use the official calibration "fudge factors" found on COISS_0011 with a slight modification for RED/CL2 filters. Early on I realized the red channel turned out consistently too bright with those factors so I worked out it needed to be multplied by 0.949 to bring it in line with other filters. The official calibration factors might indeed be off since they're quite old as a contact from PDS emailed me, in fact the whole calibration procedure was greatly improved since then. I don't have too much faith in other infrared filter factors either. Such factors weren't even derived for WAC and are missing from the calibration volume.

The color of Dione's surface in the left case suggests to me it shows the total radiance as seen by the instrument. It reminds me of my VIMS experiments without dividing by solar spectrum as sunlight is actually yellowish.
In my calibration procedure the filter transmissivities are divided by integrated solar spectrum and produce reflectance (I hope it's the right term) instead, the intrinsic color of the moon if you will. This is consistent in that it produces gray Mimas, Enceladus and gray non-stained hemispheres of Dione and Tethys. In essence the color they'd appear if shined upon by a big, white light lamp.

[MouseOnMars]

I like your page elakdawalla

Reminds me of a similiar thing I did for Themis. Apologies for the file share download, but it's all I have at the moment.

MouseOnMars

[ugordan]

It's starting to appear, the ISS volumes COISS_2026 and COISS_2027 are up, but not searchable yet. They can be accessed directly:
http://pdsimg.jpl.nasa.gov/data/cassini/ca...ter/coiss_2026/
http://pdsimg.jpl.nasa.gov/data/cassini/ca...ter/coiss_2027/

I've done a preliminary browse of the thumbnails to see if anything interesting's up. This is still the time period when Cassini was spending a lot of time on the nightside, seeing unlit rings. The real good Saturn stuff should be appearing in the Jan 1, 2008 release.

In the meantime, here are a few takeouts:

Hyperion in natural color, 2x magnified.


Iapetus in natural and IR3/GRN/UV3 color, 2x magnified. November 27, 2006.


Couple of Saturn north pole shots. A moon shadow (probably Mimas) visible near the terminator in the left image.

Titan and a lovely shot with Saturn's hazy limb showing through the translucent, unlit rings:

[elakdawalla]

I've been waiting for this!! Thanks for the notice, Gordan.

Bjorn, I'm ready to make the database update whenever you can put the tables together.

--Emily

[volcanopele]

This also means that some of my favorite SAR swaths, from T19, T20 (HiSAR over Tortola Facula), and T21 will also be released.

[Bjorn Jonsson]

The information from this ISS release is now ready for getting added to the Access database described in this thread (see this message). The database includes all of the information from the index.tab files and makes the images much easier to work with.

As before, Emily has hosted them on the same server as the database:

http://filicio.us/tpss3/files/31020/cassin...es_index_26.zip
http://filicio.us/tpss3/files/31032/cassin...es_index_27.zip

These are Excel files that must be added to the Access database as described here.

[peter59]

The ISS volumes Coiss_2026 and Coiss_2027 are now available from
PDS Planetary Rings Node in zipped form (convenient for downloading).

Coiss_2026 and Coiss_2027 in zipped form

[Bjorn Jonsson]

There is an early 'Christmas present' at the PDS: The January 1, 2008 data release (ISS and VIMS) is already there. I have managed to take a quick look at all of the ISS images and post a summary at http://www.mmedia.is/bjj/misc/css_stuff/im...s_overview.html . This also includes all of the earlier ISS data volumes.

With the exception of Titan, there are very few interesting satellite images this time, Cassini's orbit was highly inclined. The most interesting ones are probably the ones of Hyperion in coiss_2029\data\1550261798_1550410364 (mentioned by Emily in this thread).

There is heavy emphasis on the rings with lots of various movies including F ring movies, spoke movies etc. plus lots of multispectral coverage showing both the lit side and the unlit side. There are also many interesting images of Saturn, mainly WAC images. These include great images of the south pole obtained at high inclination. There are several images there that I'm going to process when I have the time (probably immediately after Christmas).

Updates to the Cassini image database (see this thread for further details) are available at the following URLs for volumes coiss_2028, coiss_2029 and coiss_2030 respectively:

http://planetary.s3.amazonaws.com/data/cas...ta/index_28.zip
http://planetary.s3.amazonaws.com/data/cas...ta/index_29.zip
http://planetary.s3.amazonaws.com/data/cas...ta/index_30.zip

[ugordan]

Lot of good stuff in this PDS release. Your summary page is very helpful, particularly before the new data becomes searchable on the PDS.
Here's a quick Saturn composite, just part of a sequence of color ring plane crossing Ian Regan animated back in the day:

[edstrick]

"....There is heavy emphasis on the rings with lots of various movies including F ring movies, spoke movies etc. plus lots of multispectral coverage ..."

My recollection is that the Voyagers got surprisingly little multispectral coverage of the rings. Imaging sequences concentrated on things like phase and inclination angle, radial structure mapping, etc, followed by the big "spoke movie" from Voyager 2 after the Voyager 1 spoke discovery.

I think I recall that one mision (maybe Voyager 1), got only orange/blue or some such 2-filter moderately high rez color coverage of the rings. I suspect there was no expectation that the rings would have widespread color variation and only minimal effort to check for radial color variations was worth the data-bandwidth.

[tedstryk]

There is definitely a large body of high phase multispectral ring data from Voyager. I am not sure about data taken on approach.

[elakdawalla]

I've made progress on my massive project to make the better images of the icy satellites more accessible to people. I'm not quite done with it -- I still need to sort out and format pages for Phoebe and the rocks, and have a bunch of introductory and explanatory text to write -- but for those of you who don't need any hand-holding to enjoy PNGified versions of every decent-sized icy satellite image in the PDS, here's the work in progress: Selected Data from Cassini's Cameras. I decided to post it now even though it's not done because I think MESSENGER may keep me too busy this week for me to do any more work on it for a bit.

--Emily

[ugordan]

Folks, just a heads up that 3 new ISS DVDs are now available at the PDS, covering a data collection period period of April 1 - June 30, 2007:

http://pdsimg.jpl.nasa.gov/data/cassini/ca...iter/coiss_2031
http://pdsimg.jpl.nasa.gov/data/cassini/ca...iter/coiss_2032
http://pdsimg.jpl.nasa.gov/data/cassini/ca...iter/coiss_2033

Just glancing through the index tables, apart from the usual assortment of Titan flyby imagery, Saturn and rings, there are some nice higher resolution multispectral observations of Dione, Tethys, Rhea and Atlas (highest res imagery throughout the mission) and also lower resolution stuff on Mimas and Iapetus (Cassini's first good look at the trailing side), Enceladus low phase observations, couple of mutuals, etc.

Also, new VIMS data is here:
http://pdsimg.jpl.nasa.gov/data/cassini/ca...er/covims_0019/

[elakdawalla]

As usual, Bjorn has created updates to the massive Cassini Image database for this latest release. For those of you who haven't seen it before, Bjorn made a Microsoft Access database containing all the metadata for all the images released by Cassini ISS to the Planetary Data System. This database is great because you can construct really quite complex queries and have it spit out lists of images that you might be interested in -- for instance, you could, if you wanted to, find all images that contain both Saturn and Titan that were taken through a RED filter, or find all images of Atlas with resolutions higher than 5 km/pixel, and so on. I use it to produce lists of files that I can then run wget on to automatically download only the images I'm interested in.

I have now created a page on the Society's website that links to the original database and all the updates. Enjoy! And don't forget to check out the pages I made that show all reasonably good images of Saturn's moons (excepting Titan) -- I haven't updated these pages yet with the April 1 release but I'll begin to work on that now that Bjorn's updated the database.

--Emily

[scalbers]

It's amazing that Emily has put these pages together for all the main icy satellites. Nice that the images appear to be more directly usable without the need for 16-bit to 8-bit conversion (or at least my viewers are doing this more easily now). I also note the sub-spacecraft lat/lon that are useful in mapping. I wonder how these were obtained since when I browse the headers on the PDS web pages I usually just see the image center point lat/lon. I see these are listed in the more complete list of header definitions on Emily's page. Just FYI, I also like to use the sub solar lat/lon info for mapping. Kudos to Bjorn as well.

Steve

[Bjorn Jonsson]

I also note the sub-spacecraft lat/lon that are useful in mapping. I wonder how these were obtained...

Everything in the database is taken from the index.tab files - there is one index.tab file for each ISS volume. These files contain a lot more data than the LBL files (or the headers in the IMG files). The database includes everything from the index.tab files.

[elakdawalla]

Here's the best icy moons and rocks stuff from the latest release. --Emily

http://www.planetary.org/data/cassini/u08q2icy/
http://www.planetary.org/data/cassini/u08q2rocks/

[Bjorn Jonsson]

The ISS images for the July-September 2007 period have hit the PDS even though July 1 is several days away. I haven't had time to look at much yet but know there's a lot of interesting stuff there. The highlights I remember are:

* The only targeted Iapetus flyby
* A 5000 km nontargeted Rhea flyby
* A very nice flyby of Dione (~40,000 km IIRC)
* Lots of nice Tethys images
* Several Titan flybys

[ugordan]

Ooh, nice catch, Bjorn. I was checking it myself earlier today and no luck. This is as fresh as it gets

[elakdawalla]

Iapetus!!!! I can't believe it's been long enough since that flyby that the data is on the PDS already. I can't wait to see what you guys produce from that data set.

I'm looking forward to downloading stuff -- but probably can't get to it until this weekend. Bjorn, I'm ready for the database update whenever you get around to it.

--Emily

[ugordan]

A taste of Iapetus data, from the Saturn system PR sequence before C/A. RGB color:

I forgot which star that was to the above right of Iapetus and also apparently another one off the sunlit crescent.

EDIT: Quick regional RGB color on the outbound part and one of the parting shots on the right at 2x:


The dark stuff truly is remarkably gray on the trailing hemisphere. I'm now wondering whether my plan for redoing the big outbound mosaic in approx. natural color is worth the trouble just to get essentially b/w imagery in the end. There are still odd false color high-res mosaics here and there, though, that weren't released officially.

[elakdawalla]

Ooh! An amuse bouche if I ever tasted one

--Emily

[charborob]

Ooh! An amuse bouche if I ever tasted one

In French, the word is "amuse-gueule". I agree with you: very tasty.

[ugordan]

Another tidbit from the release: an approx. natural color ring scan of the left ansa, consisting of 5 NAC RGB segments. This was taken a couple of days (Sep 7 IIRC) before the Iapetus encounter and shows a similar vantage point. There's also the right ansa data at the PDS, but it doesn't show as much interesting stuff (Mimas, Pan and Prometheus).

[Ant103]

I am wondering how can I decode PDS ".img" file on my mac. I have OS 10.5.3 and before, on my old pc, I have found a Gimp plugin to read .IMG files. Gimp 2.4 run on OS 10.5, but, the plugin is not compiled and I don't know how to do . This is for Gimp, but, I imagine that there are other solution .
Doug : you are on a mac, how do you do?

[djellison]

I use a PC

Seriously - I do - img2png on my desktop PC machine.

My MacBookPro is my 'life' machine (Email, calender, presentations, photos etc), my PC desktop is my 'power' machines (storage, PTGui, cold hard data, 3d rendering, Photoshop)

Doug

[Bjorn Jonsson]

And now when I am at last ready to start large scale downloading Murphy's law strikes and I cannot access the PDS imaging node. I guess I'm not the only one...

[elakdawalla]

Blerg. I can't access it either.

--Emily

[ugordan]

I find that the PDS site is unavailable all too often. I'm not sure if it's a maintenance thing, but weekends usually seem to be iffy. Very annoying.

[stevesliva]

Another tidbit from the release: an approx. natural color ring scan of the left ansa, consisting of 5 NAC RGB segments. This was taken a couple of days (Sep 7 IIRC) before the Iapetus encounter and shows a similar vantage point. There's also the right ansa data at the PDS, but it doesn't show as much interesting stuff (Mimas, Pan and Prometheus).

I love this shot! Mimas is posed perfectly, and Pan and Prometheus... just amazing.

[elakdawalla]

I just exchanged emails with some folks at the PDS. They know about the problem, has something to do with an expired something-or-other on a server so access isn't currently permitted; they hoped the problem would be resolved some time today.

--Emily

[ugordan]

Looks like they need a mission extension as well.

[DrShank]

Looks like they need a mission extension as well.

took advantage last week and downloaded and calibrated everything. i should have the geometry
corrected next week sometime, while i tour china....
wow stuff!
paul

[ugordan]

You're just trying to make us jealous. Admit it.

[peter59]

I just exchanged emails with some folks at the PDS. They know about the problem, has something to do with an expired something-or-other on a server so access isn't currently permitted; they hoped the problem would be resolved some time today.

--Emily

Problem resolved, site is available. Vol. Coiss_2034 - Coiss_2037 released.

[peter59]

The ISS volumes Coiss_2034, Coiss_2035, Coiss_2036 and Coiss_2037 are now available from PDS Planetary Rings Node in tar.gz form (convenient for downloading, even with a 4:1 compression ratio).

COISS_2034.tar.gz - 1208 MB
COISS_2035.tar.gz - 1026 MB
COISS_2036.tar.gz - 1117 MB
COISS_2037.tar.gz - 167 MB

Volumes Coiss_2034, Coiss_2035, Coiss_2036 and Coiss_2037 in tar.gz format

[volcanopele]

Still waiting for all the RADAR swaths to return.

[elakdawalla]

Björn sent me these last week and I finally posted them: the Excel updates for the latest four volumes for his Access database to all Cassini images. Download from here.
--Emily

[elakdawalla]

After living with the browse pages I'd made for the Cassini PDS images, I decided I didn't like them, so I am trying out a new design, more like the one I did for the RAC pages. Please check out my new index to all reasonably good Cassini images of Enceladus and let me know what you think; after a little input I'll go ahead and do these for the rest of the moons. (An example of my old design is here.)

To whet your appetite, here's some plumes from rev 50.


--Emily

[Stu]

That looks brilliant Emily, a really useful resource I think. I know for a fact I haven't got the imaging skills or tech savvy to make any real practical use of it, but others here - and elsewhere - will, and they'll appreciate all your hard work and effort I'm sure. It is a lot neater and more easily navigable than v1.0. Great seeing all the plumes images in one place, really brings home just how fascinating and important a moon Enceladus is.

[jasedm]

Agreed - and nine days until the next sub-50km flyby, featuring amongst other things, some close-ups of the plume vents

[elakdawalla]

I know for a fact I haven't got the imaging skills or tech savvy to make any real practical use of it...

Hmm. It's kind of distressing to hear you say that -- this is intended to serve the same function as the raw images pages for Cassini, or the Phoenix mission, or whatever, except that it is supposed to provide access to much higher-quality, non-JPEGgy, non-contrast-stretched data that's archived in a way that makes it tough for amateurs to access. I'm trying to solve that access problem and make these much better data available to the public. You can do all the same stuff with these images that you can do with the raw Cassini images, you just aren't hobbled by the limitations of the raw data site. Clearly I need to do something to make this more accessible to you -- what do I need to do?

--Emily

[Stu]

Sorry Emily, that came out wrong! I meant use it in the same way that our experts here - ugordan, james, etc - will use it, i.e. making elaborate mosaics and finely colour- and level-balanced images. I don't have the software, experience (or patience!) to create the masterpieces they do. But I will definitely be using it to make simpler RGB composites and to pull details out of images of plumes and surface features, for use in my Outreach talks, and have already started on a couple of images today for use in my astro soc meeting on Monday night...

[Bjorn Jonsson]

I'm resurrecting this old thread to announce a new version of the database discussed earlier in the thread. All of the errors I mentioned there have been fixed and the database includes information for all of the ISS images released to the PDS so far (almost 200,000 images).

As earlier Emily has provided hosting for this big file (it's about 85 MB zipped). Further information is available here:
http://planetary.org/explore/topics/cassin...s_database.html

[Bjorn Jonsson]

I just noticed that the January 1, 2008 ISS PDS release is already there. What's more, there is now a compressed (GZ) file available for each volume. This is a very welcome addition - it reduces the amount of data to download and more importantly, download errors now manifest themselves as error messages during decompression. This is very important as I have discovered a few cases where files got corrupt during downloading without any error messages appearing during the download. Because of this I may even gradually redownload everything I have previously downloaded, this time as GZ files.

I haven't downloaded anything yet but now I know this weekend is going to be a 'download weekend' .

[elakdawalla]

*Glub glub glub*

That's the sound of Emily drowning in data. I haven't even wrapped my mind around the last PDS release yet! Not that I'm complaining.

--Emily