This version should not be used. It has been replaced by the download_chandra_obsid script that is part of the CIAO contributed scripts package.
Both PDF and plain text versions of this document are available.
download_chandra_obsid is a simple command-line script that allows a user to download public data from Chandra by giving a list of Observation Ids. The files are downloaded to the current working directory, and stored using the same layout as the Chandra archive; for example, ObsId 1843 would be stored in
1843/...
1843/primary/...
1843/secondary/...
An optional list of file types can be given, which restricts the data to be downloaded (by default all available data for the Observation Id is downloaded).
As described below, this script is not an official product of the CXC and is provided with no support. Please use the version provided with CIAO as part of the contributed scripts package.
This is version 2010.05.04 of download_chandra_obsid. It should not be used as it has been replaced by a version
provided with CIAO.
download_chandra_obsid)2010.05.04)The only file you need to download is the script itself, namely download_chandra_obsid.
The script is written in Python and should work using the CIAO-provided version (CIAO 4.2 provides version 2.6.2). There has been limited testing of the script using version 2.5.1 of Python.
If it is given the executable bit - e.g.
unix% chmod u+x download_chandra_obsid
then it can be run as a normal UNIX command, or you can say
unix% python download_chandra_obsid
The script can be renamed if you object to typing such a long name; for instance to get_obsid.
The examples below assume that the script is in the current working directory, but it can be placed anywhere, such as one of the directories in your $PATH.
unix% ./download_chandra_obsid 1843
The data will be stored in the directory 1843/ and will contain all available data.
unix% ./download_chandra_obsid 1842,1843
To download multiple ObsIds you can run the tool multiple times or use a comma-separated list as shown above. In this example the data will be stored in the directories 1842/ and 1843/.
Note that the ObsId values do not need to be listed in ascending order.
unix% ./download_chandra_obsid 1843 fov,bpix,evt1,flt
Here only the FOV, BPIX, EVT1 and FLT files will be downloaded. The data will be stored in the relevant directores within 1843/ (they will be created if need be).
unix% ./download_chandra_obsid 1843,1842 fov,bpix,evt1,flt
Here we download the FOV, BPIX, EVT1 and FLT files for the Observation Ids 1842 and 1843.
A help message will be displayed if the --help option is used, or the script is called with either no arguments or invalid input. The message is shown below:
unix% ./download_chandra_obsid
Usage: download_chandra_obsid <obsid1>,..,<obsidN> [<type1>,..,<typeN>]
Download public Chandra observations. The observations to download are given
as a comma-separated list of ObsId numbers, and an optional comma-separated
list of file "types" can also be given, which will only download files that
contain the type strings. So an argument of '1842,1843' will download all data
for the obs ids 1842 and 1843, whereas '1842,1843 fov,vv,evt2' will only
download the V&V, fov, and evt2 files for these observations. The data is
written to the current directory, with each obsid being saved to its own
directory (following the layout used by the Chandra archive).
Options:
-h, --help show this help message and exit
-q, --quiet Download the files without any screen output? [default:
False]
-v, --version List the version of the script and exit.
-c, --copyright List the copyright for the script and exit.
-t, --filetypes List the valid file types and exit.
-d, --debug Display diagnostic output? [default: False]
In this document the long names of the options will be used, such as --help, although the short versions listed above (e.g. -h) can also be used.
The --filetypes option lists the valid names for the optional type argument:
unix% ./download_chandra_obsid --filetypes
The list of valid file types is:
aoff aqual asol bias bpix cntr_img dtf eph0 eph1 evt1 evt2 flt fov
full_img msk mtl oif osol pbk pha2 plt soff src2 src_img stat sum vv
The Chandra Data Products guide provides more information on these files, including their uses (although there is no guarantee that the names agree exactly).
The --version option displays the version of the script, which is the release date in YYYY.MM.DD format:
unix% ./download_chandra_obsid --version
2010.05.04
The default behavior is to display output as each file is downloaded, as shown below. To turn this off use the --quiet flag, which will restrict screen output to error messages.
When run, the tool will appear to pause as it checks what data is available in the archive for the ObsId value, and then print a banner listing the total size available before listing each file as it is downloaded:
unix% ./download_chandra_obsid 1842
Downloading files for ObsId 1842, total size is 69 Mb.
Type Format Size 0........H.........1 Download Time Average Rate
---------------------------------------------------------------------------
vv pdf 88 Kb #################### < 1 s 1910.5 kb/s
oif fits 23 Kb #################### < 1 s 744.5 kb/s
sum html 2 Kb #################### < 1 s 58.1 kb/s
sum ps 2 Mb #################### 4 s 655.9 kb/s
sum html 4 Kb #################### < 1 s 199.2 kb/s
sum html 3 Kb #################### < 1 s 215.1 kb/s
cntr_img fits 229 Kb #################### < 1 s 5794.9 kb/s
cntr_img jpg 826 Kb #################### < 1 s 7064.9 kb/s
evt2 fits 19 Mb #################### 3 s 5504.3 kb/s
full_img fits 90 Kb #################### < 1 s 2964.0 kb/s
full_img jpg 68 Kb #################### < 1 s 1613.4 kb/s
src2 fits 14 Kb #################### < 1 s 595.3 kb/s
src_img jpg 70 Kb #################### < 1 s 1417.6 kb/s
bpix fits 10 Kb #################### < 1 s 692.3 kb/s
fov fits 6 Kb #################### < 1 s 414.4 kb/s
eph1 fits 281 Kb #################### < 1 s 6248.2 kb/s
asol fits 2 Mb #################### < 1 s 2878.2 kb/s
aoff fits 889 Kb #################### < 1 s 7823.0 kb/s
evt1 fits 36 Mb #################### 6 s 5826.7 kb/s
flt fits 16 Kb #################### < 1 s 953.1 kb/s
msk fits 5 Kb #################### < 1 s 247.2 kb/s
mtl fits 334 Kb #################### < 1 s 5525.9 kb/s
soff fits 4 Kb #################### < 1 s 296.1 kb/s
stat fits 276 Kb #################### < 1 s 6394.4 kb/s
bias fits 426 Kb #################### < 1 s 7284.0 kb/s
bias fits 494 Kb #################### < 1 s 7877.3 kb/s
bias fits 430 Kb #################### < 1 s 7451.4 kb/s
bias fits 423 Kb #################### < 1 s 7303.9 kb/s
bias fits 427 Kb #################### < 1 s 6923.7 kb/s
bias fits 427 Kb #################### < 1 s 7491.6 kb/s
pbk fits 4 Kb #################### < 1 s 280.3 kb/s
vv pdf 2 Mb #################### < 1 s 3041.0 kb/s
eph1 fits 6 Kb #################### < 1 s 312.2 kb/s
eph1 fits 274 Kb #################### < 1 s 601.0 kb/s
eph1 fits 258 Kb #################### < 1 s 5872.6 kb/s
osol fits 356 Kb #################### < 1 s 5526.5 kb/s
aqual fits 132 Kb #################### < 1 s 3816.4 kb/s
osol fits 360 Kb #################### < 1 s 5935.3 kb/s
Total download size for ObsId 1842 = 69 Mb
Total download time for ObsId 1842 = 17 s
The first three columns give the filetype, format and file size of the file. The fourth column indicates the fraction of the file that has been downloaded (each # mark is 5% of the file size, with the H symbol in the column header indicating the 50% point) and is updated as the file is downloaded. The last two columns are added once the file size and list the download time and average download rate for that file. A summary of the download is provided once all the files for an ObsId are downloaded.
The tool will skip any files that have previously downloaded, so it is safe to halt the download during a run (using control-c) and then re-start it. Any partially-downloaded files will resume, so you do not need to re-download data you already have.
This allows you to do partial downloads, for example:
unix% ./download_chandra_obsid 1843 evt2,fov
Downloading files for ObsId 1843, total size is 17 Mb.
Type Format Size 0........H.........1 Download Time Average Rate
---------------------------------------------------------------------------
evt2 fits 17 Mb #################### 6 s 2905.2 kb/s
fov fits 6 Kb #################### < 1 s 428.0 kb/s
Total download size for ObsId 1843 = 17 Mb
Total download time for ObsId 1843 = 6 s
unix% ./download_chandra_obsid/download_chandra_obsid 1843 bpix,evt2
Downloading files for ObsId 1843, total size is 17 Mb.
Type Format Size 0........H.........1 Download Time Average Rate
---------------------------------------------------------------------------
evt2 fits 17 Mb already downloaded
bpix fits 11 Kb #################### < 1 s 779.5 kb/s
Total download size for ObsId 1843 = 11 Kb
Total download time for ObsId 1843 = < 1 s
and then just download the whole observation - e.g. ./download_chandra_obsid 1843 - without having to worry about wasting time on files that you already have.
The tool does not check that you have an uncompressed version of an archive file, so in the 1843 output above, if you uncompress the evt2 file and then re-run the script the compressed version of the file will be re-downloaded.
There is no check that files have been corrupted during the download.