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' .

[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?

[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.