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Unmanned Spaceflight.com _ Cometary and Asteroid Missions _ 2 Pallas

Posted by: tedstryk Sep 13 2008, 01:10 AM

We have seen two resolved views of Pallas on UMSF. One was my processing of the May 2001 snapshot (which missed the PC chip in WFPC/2), and the other was a lone frame published in Russell et al's abstract.

Here they are in respective order

Well, the whole HST rotation sequence has now been released. I plan to have a crack at it, but I have so many irons in the fire, I figured I would post the link so everyone can have at it.

http://archive.stsci.edu/proposal_search.php?mission=hst&id=11115

Happy processing!

Posted by: 3488 Sep 13 2008, 01:34 PM

Thanks Ted,

I tried downloading them but it didn't work.

Are there JPEG, Gif or preferably BMP of the 2 Pallas images?

I assume no moons have been found orbiting the giant asteroid (if so it would be mentioned in the general astronomical press / sites)?

2 Pallas has in my opinion been a bit of a Cinderella regarding the real big asteroids, the largest in the Main Belt if you do not consider 1 Ceres to be an asteroid, rather Dwarf Planet.

I hope the option with DAWN has not been abandoned in December 2018, when 2 Pallas may be reachable during the descending node (assuming primary mission at 4 Vesta & 1 Ceres is successful).

I looks like that there may be two large craters or basins on the right hand image. 2 Pallas will not be boring for sure.

Hopefully 2 Pallas is high on the list of the new WF/PC 3 & repaired ACS?

Once again, thank you very much Ted for the tip off. It is very much appreciated.

Andrew Brown.

Posted by: jamescanvin Sep 13 2008, 01:55 PM

QUOTE (3488 @ Sep 13 2008, 02:34 PM)

Are there JPEG, Gif or preferably BMP of the 2 Pallas images?

I think that is what Ted is suggesting people 'have a crack at'. Process the data to make pretty images we can all look at.

It's been a long time since I touched any HST data, I may have to have a look to see if I can dust off any old scripts.

James

Posted by: elakdawalla Sep 13 2008, 07:49 PM

Björn modified IMG2PNG when the New Horizons data was released last year to be able to process FITS, spitting out all the image planes separately, and logging (in a file called img2png.log) the min and max values to be found in each plane; you can use a config file to stretch each plane individually. Here's the email he sent me about it, most but not all of which is relevant here.

QUOTE

I'm attaching an experimental version of IMG2PNG that should be able to convert FITS files to PNGs. This version also includes the file cfitsio.dll that should be placed in the same directory as img2png.exe.
I recommend renaming the old version of IMG2PNG in case this one doesn't work properly.

There is one new feature associated with the FITS->PNG conversion: The optional -ct ("contrast table") command line switch. This command line switch allows you to specify a file containing the contrast stretch that will be applied to each image that gets converted. For example, the attached file (lorri_contrast_table.txt) looks like this:

0 3800
0 25
0 32

This means that for image 1 in every FITS file, pixels with intensity <=0 will be set to black in the output file and pixels with intensity >=3800 will be set to white. The 0 and 25 parameters apply to image 2 in each FITS file and 0 and 32 to image 3. The file can contain more rows, for example you want 4 rows for the MVIC images. This feature allows you to use the same contrast stretch parameters for all of the FITS files that get converted. If -ct is not specified the contrast strecth applied depends on the min/max intensity for the individual files. Any of the numbers in the file can be replaced with a "-"
(without quotes), meaning use the minimum intensity value (if "-" is specified instead of a minimum value) to determine the contrast stretch.
Replacing the maximum value with a "-" has a comparable effect.

Regarding command line switches, at the moment only -t and -ct can be used when converting FITS files. Actually -ct can only be used when converting FITS files, for other files it is ignored. If you are unsure of which values to use for the contrast stretch start by running IMG2PNG without using -ct. When all of the files have been converted IMG2PNG prints out a list of min/max values for the images found in the FITS files (for the LORRI images this this list will contain 3 pairs of min/max values). What all of this means is that you probably want all of the FITS files to contain the same number of images (use two separate conversion runs for converting LORRI and MVIC data).

In addition to this, the "-n" switch also works, so you can use IMG2PNG to run through the FITS files and examine their min and max pixel values, spitting them to the log file, without taking the time to do the actual format conversion.

I downloaded the first of the listed sets, ran it through IMG2PNG and it looks to me like this one might be Pallas. Several pixels, but not the most impressive photo...

--Emily

Posted by: 3488 Sep 13 2008, 10:04 PM

Hi Emily,

Did New Horizons image 2 Pallas from afar during the passage of the asteroid belt? Would have been a great test of the LORRI. Or have I misunderstood what you were saying? Most likely.

Hi all,

Had a go at bringing out more detail from the 2 Pallas HST image that Ted posted on the right.

There are definitely some features visible, no doubt.

I hope some image panels of a 2 Pallas rotation will be made up, like those already done for 1 Ceres & 4 Vesta. Also 2 Pallas has some weird seasons, owing to its almost tipped over rotation like Uranus & Asteroid 433 Eros.

The best time to observe the whole of 2 Pallas obviously through a complete rotation would be around the Palladian Equinoxes, though other times would be better for the higher latitudes & polar regions.

Andrew Brown.

Posted by: Decepticon Sep 14 2008, 07:10 PM

After HST gets its Tune Up can we expect any improvement on Ceres Pallas and vesta resolutions?

Posted by: tedstryk Sep 14 2008, 08:27 PM

QUOTE (Decepticon @ Sep 14 2008, 08:10 PM)

After HST gets its Tune Up can we expect any improvement on Ceres Pallas and vesta resolutions?

ACS already imaged Ceres, but it could definitely do better with Vesta and Pallas. The question is whether or not such observations are worked in.