How to download Chandra Data from the Archive
![[CXC Logo]](../../imgs/cxc-logo.gif){kind=logo}
CIAO 4.15 Science Threads
Overview
Synopsis:
The Chandra Data Archive contains all the data obtained with the Chandra telescope.
This thread explains the two Data Archive interfaces, ChaSeR and the Chandra footprint service. Additionally, there are command-line scripts for finding and downloading publicly-available Chandra data from the Archive: find_chandra_obsid and download_chandra_obsid. Please note that proprietary data can only be accessed using ChaSeR.
Purpose:
To illustrate several methods of downloading ObsID 1843 (ACIS-I, G21.5-0.9), which is used in the Introductory CIAO Threads.
Related Links:
Last Update: 30 Jun 2022 - Update some broken links.
Contents
- What data files do I need for my analysis?
- Using the find_chandra_obsid script
- Using the download_chandra_obsid script
- Using ChaSeR
- Chandra Footprint Service
- Chaser downloadable application(retired)
- URL and Unpack the Data
- History
-
Images
- Figure 1: The completed ChaSeR form to search for ACIS-I observations of G21.5-0.9
- Figure 2: The ChaSeR Search Results page
- Figure 3: ChaSeR package selection
- Figure 4: ChaSeR retrieval list
- Figure 5: Retrieval Results screen
- Figure 6: Starting a search for G21.5-0.9 with the Chandra Footprint Service
- Figure 7: The result of the search for G21.5-0.9 with the Chandra Footprint Service
- Figure 8: A quick look at the data
- Figure 9: Showing just the HRC-S observations
- Figure 10: Filtering the results with the Chandra Footprint Service
- Figure 11: The information for ObsId 1843
What data files do I need for my analysis?
If you are unsure what types of analysis you will be doing, downloading both the primary and secondary data packages will ensure that you will have any file you might need.
The standard data distribution arranges the data products such that the products necessary for most analyses (e.g. the CIAO threads) are in the primary directory. If you are interested in reprocessing your data, for example, you will also need the level 1 files, which are in the secondary directory.
![[IMPORTANT]](../../imgs/important.png)
The CXC strongly encourages users to reprocess their data to ensure that they have the latest calibrations consistent with the current CALDB.
Users should run chandra_repro or follow the step by step instructions the Reprocessing Data to Create a New Level=2 Event File thread.
Each of the threads also includes a list of the specific files needed to run it.
Using the find_chandra_obsid script
The find_chandra_obsid script lets you search the publicly-available data in the Chandra Data Archive from the command line. It can be used to search by object name - using the CADC Name Resolver - or by position. First we try by name, but find that the resolver does not recognize the name:
unix% find_chandra_obsid G215-09 # find_chandra_obsid (12 November 2015): ERROR No position found matching the name 'G215-09'.
so we give the source location explicitly (as there are many matches for this calibration target most have them have been removed from the display below); note that the declination value includes both ' and " characters which involves an awkward combination in this tcsh example
unix% find_chandra_obsid "18h 33m 33.50s" "-10d 34' 06.70"'"' # obsid sepn inst grat time obsdate piname target 142 0.0 HRC-I NONE 30.5 2000-02-16 Calibration G21.5-0.9 143 0.0 HRC-I NONE 15.2 1999-09-04 Calibration "G21.5-0.9 [HRC-I, Offsets=0,0,0]" 144 0.0 HRC-I NONE 30.2 2000-09-01 Calibration "G21.5-0.9 [HRC-I, Offsets=0,0,0]" 158 0.0 ACIS-I NONE 9.8 1999-08-25 Calibration "G21.5-0.9 [Chip I1, T=100, Offsets=-3,-5,0 Off-ax]" 159 0.0 ACIS-S NONE 15.0 1999-08-23 Calibration "G21.5-0.9 [Chip S3, T=100, Offsets=0,0,0 Std Cand]" 160 0.0 ACIS-I NONE 9.8 1999-08-25 Calibration "G21.5-0.9 [Chip I0, T=100, Offsets=5,-5,0 Off-ax]" 161 0.0 ACIS-I NONE 9.8 1999-08-25 Calibration "G21.5-0.9 [Chip I2, T=100, Offsets=5,3,0 Off-ax]" 162 0.0 ACIS-I NONE 13.2 1999-08-27 Calibration "G21.5-0.9 [Chip I3, T=100, Offsets=-1,1,0 Std Can]" 163 23.5 ACIS-S NONE 10.0 1999-08-15 Calibration "G21.5-0.9 [Chip S0, T=100, Offsets=23,0,0]" 164 15.0 ACIS-S NONE 9.8 1999-08-15 Calibration "G21.5-0.9 [Chip S1, T=100, Offsets=15,0,0]" 165 0.0 ACIS-S NONE 9.8 1999-08-23 Calibration "G21.5-0.9 [Chip S2, T=100, Offsets=6,0,0]" ... 1840 0.0 ACIS-S NONE 7.8 2000-09-02 Calibration "G21.5-0.9 [Chip S3, T=120, Offsets=-1,5,-4]" 1841 0.0 ACIS-I NONE 8.1 2000-09-01 Calibration "G21.5-0.9 [Chip I3, T=120, Offsets=-1,10,5]" 1842 0.0 ACIS-I NONE 7.5 2000-09-02 Calibration "G21.5-0.9 [Chip S3, T=120, Offsets=-1,15,0]" 1843 0.0 ACIS-I NONE 8.0 2000-09-02 Calibration "G21.5-0.9 [Chip S3, T=120, Offsets=-1,20,-4]" ...
Positions can be supplied in a range of common formats for RA and Dec - e.g. as decimal degrees or various sexagesimal forms - as shown in further examples.
There are several ways to filter this output:
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Use the limited filtering capabilities of the script (the instrument and grating parameters):
unix% find_chandra_obsid 278.390 -10.57 instrument=hrci # obsid sepn inst grat time obsdate piname target 142 0.1 HRC-I NONE 30.5 2000-02-16 Calibration G21.5-0.9 143 0.1 HRC-I NONE 15.2 1999-09-04 Calibration "G21.5-0.9 [HRC-I, Offsets=0,0,0]" 144 0.1 HRC-I NONE 30.2 2000-09-01 Calibration "G21.5-0.9 [HRC-I, Offsets=0,0,0]" 1406 0.1 HRC-I NONE 30.1 1999-10-25 Calibration "G21.5-0.9 [HRC-I, Offsets=0,0,0]" ...
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Write the output to a file and then use the CIAO DataModel tools; for example:
unix% find_chandra_obsid 18:33:33.5 -10:34:7 > matches.txt unix% dmlist matches.txt counts 128 unix% dmlist matches.txt"[sepn<1,inst=ACIS-I]" counts 42 unix% dmlist matches.txt"[sepn<1,inst=ACIS-I,time>10][cols obsid,time]" data,clean # obsid time 162.0 13.10 1233.0 14.0The detail parameter can be changed to the all setting to have more columns written out (e.g. the target position), or obsid if you only want the observation id.
Once you have the observation ids you want you can use download_chandra_obsid to download them. Alternatively you can set the download parameter of the script to be asked whether each matching ObsId should be downloaded (download=ask), or to automatically download all matching ObsIds (download=all). The latter option should be used carefully as it is easy to accidentally download a lot of data!
As an example, here we look for HRC-I observations to download; the list of matching observations is given and then we are asked whether we wish to download each set:
unix% find_chandra_obsid '18 33 34' '-10 34' inst=hrci download=ask
There were 18 matching observations:
1/18: Obsid=142 Sepn=0.2 Inst=HRC-I Grat=NONE Exp=30.5 ObsDate=2000-02-16
PI=Calibration Target=G21.5-0.9
2/18: Obsid=143 Sepn=0.2 Inst=HRC-I Grat=NONE Exp=15.2 ObsDate=1999-09-04
PI=Calibration Target=G21.5-0.9 [HRC-I, Offsets=0,0,0]
...
17/18: Obsid=10648 Sepn=0.2 Inst=HRC-I Grat=NONE Exp=10.2 ObsDate=2009-02-17
PI=Calibration Target=G21.5-09
18/18: Obsid=13091 Sepn=0.2 Inst=HRC-I Grat=NONE Exp=10.2 ObsDate=2011-05-30
PI=Calibration Target=G21.5-09
Use h to get help on the download options.
1/18: Obsid=142 Sepn=0.2 Inst=HRC-I Grat=NONE Exp=30.5 ObsDate=2000-02-16
PI=Calibration Target=G21.5-0.9
Download [y, n, q, a, h]: h
Download options are:
y - download this ObsId
n - do not download this ObsId
q - do not download this or the remaining 17 ObsIDs
a - download this ObsId and the remaining 17 ObsIDs
h - display this information
Download [y, n, q, a, h]: n
2/18: Obsid=143 Sepn=0.2 Inst=HRC-I Grat=NONE Exp=15.2 ObsDate=1999-09-04
PI=Calibration Target=G21.5-0.9 [HRC-I, Offsets=0,0,0]
Download [y, n, q, a, h]:
...
From this point you can decide whether to download each observation, and once this is finished the download will begin.
find_chandra_obsid also accepts an OBS_ID value and will locate any other observations that overlap it.
unix% find_chandra_obsid 1843 # obsid sepn inst grat time obsdate piname target 142 0.0 HRC-I NONE 30.5 2000-02-16 Calibration G21.5-0.9 143 0.0 HRC-I NONE 15.2 1999-09-04 Calibration "G21.5-0.9 [HRC-I, Offsets=0,0,0]" 144 0.0 HRC-I NONE 30.2 2000-09-01 Calibration "G21.5-0.9 [HRC-I, Offsets=0,0,0]" 146 0.0 HRC-S NONE 10.5 2000-02-16 Calibration "G21.5-0.9 [HRC-S, Offsets=0,0,0 CENTER MCP]" 147 0.0 HRC-S NONE 9.7 1999-09-05 Calibration "G21.5-0.9 [HRC-S, Offsets=0,0,0 CENTER MCP]" 148 0.0 HRC-S NONE 10.1 2000-08-31 Calibration "G21.5-0.9 [HRC-S, Offsets=0,0,0 CENTER MCP]" 150 0.0 HRC-S NONE 10.5 2000-02-16 Calibration "G21.5-0.9 [HRC-S, Offsets=-30,0,0 +Y MCP]" 151 0.0 HRC-S NONE 9.8 1999-09-05 Calibration "G21.5-0.9 [HRC-S, Offsets=-20,0,0 +Y MCP]" 152 0.0 HRC-S NONE 10.5 2000-08-31 Calibration "G21.5-0.9 [HRC-S, Offsets=-30,0,0 +Y MCP]" 154 0.0 HRC-S NONE 10.1 2000-02-16 Calibration "G21.5-0.9 [HRC-S, Offsets=30,0,0 -Y MPC]" 155 0.0 HRC-S NONE 10.5 2000-08-31 Calibration "G21.5-0.9 [HRC-S, Offsets=30,0,0 -Y MPC]" 158 0.0 ACIS-I NONE 9.8 1999-08-25 Calibration "G21.5-0.9 [Chip I1, T=100, Offsets=-3,-5,0 Off-ax]" 159 0.0 ACIS-S NONE 15.0 1999-08-23 Calibration "G21.5-0.9 [Chip S3, T=100, Offsets=0,0,0 Std Cand]" ...many more...
Using the download_chandra_obsid script
The download_chandra_obsid script provides a simple command-line interface to the Chandra Data Archive. It requires only the ObsID that you wish to download:
unix% download_chandra_obsid 1843
Each file that is downloaded will be displayed on screen, giving the type, format, and filesize before a progress bar of # marks (each # mark indicates 10% of the file). Once the file has been downloaded, an average rate is displayed for the download. (This output can be turned off with the "-q" or "--quiet" flags.)
Downloading files for ObsId 1843, total size is 80 Mb.
Type Format Size 0........H.........1 Download Time Average Rate
---------------------------------------------------------------------------
evt1 fits 35 Mb #################### 3 s 13680.7 kb/s
vvref pdf 19 Mb #################### < 1 s 63083.8 kb/s
evt2 fits 17 Mb #################### < 1 s 57310.5 kb/s
asol fits 2 Mb #################### < 1 s 35308.9 kb/s
cntr_img jpg 833 Kb #################### < 1 s 28705.2 kb/s
bias fits 496 Kb #################### < 1 s 26445.9 kb/s
bias fits 430 Kb #################### < 1 s 19840.9 kb/s
bias fits 427 Kb #################### < 1 s 20806.9 kb/s
bias fits 427 Kb #################### < 1 s 16715.5 kb/s
bias fits 426 Kb #################### < 1 s 23607.6 kb/s
bias fits 424 Kb #################### < 1 s 21356.9 kb/s
osol fits 353 Kb #################### < 1 s 19716.8 kb/s
osol fits 351 Kb #################### < 1 s 18620.1 kb/s
mtl fits 342 Kb #################### < 1 s 16135.6 kb/s
osol fits 341 Kb #################### < 1 s 15936.4 kb/s
stat fits 291 Kb #################### < 1 s 17667.2 kb/s
eph1 fits 281 Kb #################### < 1 s 18277.9 kb/s
eph1 fits 274 Kb #################### < 1 s 16063.1 kb/s
eph1 fits 258 Kb #################### < 1 s 11761.5 kb/s
cntr_img fits 168 Kb #################### < 1 s 9158.6 kb/s
aqual fits 148 Kb #################### < 1 s 11467.8 kb/s
full_img jpg 85 Kb #################### < 1 s 7066.2 kb/s
full_img fits 62 Kb #################### < 1 s 5244.6 kb/s
vv pdf 42 Kb #################### < 1 s 4129.4 kb/s
oif fits 20 Kb #################### < 1 s 2021.3 kb/s
bpix fits 18 Kb #################### < 1 s 1710.9 kb/s
readme ascii 10 Kb #################### < 1 s 819.0 kb/s
fov fits 8 Kb #################### < 1 s 639.7 kb/s
flt fits 6 Kb #################### < 1 s 630.6 kb/s
eph1 fits 6 Kb #################### < 1 s 636.1 kb/s
msk fits 5 Kb #################### < 1 s 541.4 kb/s
pbk fits 4 Kb #################### < 1 s 399.2 kb/s
Total download size for ObsId 1843 = 80 Mb
Total download time for ObsId 1843 = 4 s
The script also allows you to download multiple ObsIDs at one time by supplying a comma-separated list:
unix% download_chandra_obsid 1842,1843,459
or to download selected data files:
unix% download_chandra_obsid 1842,1843 evt2,asol
Refer to the help file for further details.
The data files are now ready to be used in CIAO. For a description of the files, read the Introduction to the Data Products thread.
Using ChaSeR
ChaSeR is the web interface to the Chandra Data Archive. It allows users to browse the observation catalog with a variety of search criteria, to display preview images, and to download the data tarfiles.
ChaSeR allows users to download the standard primary and secondary packages. It also allows user to download individual files from those package, and provides access to lower level data products (Level 0) as well as proprietary and engineering observations.
1. Browse
Chandra Archive data may be browsed using any of the fields in ChaSeR, such as Target Name, Instrument, Grating, ObsID, and Category. Since we are interested in an ACIS-I observation of G21.5-0.9, highlight the appropriate Instrument (ACIS-I) and Grating (NONE) and enter the Target Name. In the "Customize Output" section at the bottom of ChaSeR, change the Sort Order to "Observation ID".
Figure 1 shows the completed form.
Figure 1: The completed ChaSeR form to search for ACIS-I observations of G21.5-0.9
![[Thumbnail image: The Instrument (ACIS-I) and Grating (NONE) options are highlighted in the ChaSeR webpage and the Target Name is set to "G21.5-0.9".]](webform.png)
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Figure 1: The completed ChaSeR form to search for ACIS-I observations of G21.5-0.9
Searching for ACIS-I observations of G21.5-0.9.
Click the "Search" button in the upper left corner of the form to start the search.
2. Select
The Search Results window brings up all the observations that match our search criteria, as shown in Figure 2.
Figure 2: The ChaSeR Search Results page
![[Thumbnail image: The Search Results page lists all results of the search for ACIS-I observations of G21.5-0.9]](webmatch.png)
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Figure 2: The ChaSeR Search Results page
Search results may be sorted by the "Order By..." menu.
The default number of rows returned in ChaSeR is 50. If your search matches more than 50 observations, a message will be shown in the bottom left of the results page: 99 observations found, 50 displayed in this screenshot (Figure 2). Use the "Change Search Criteria" link to narrow the search or to increase the Row Limit value.
Click on ObsID 1843 to highlight the row. After doing so one may:
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Use the "Details" link to display specifics about the observation, e.g. general observation parameters, ACIS-specific parameters, and any observation contraints.
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Use the "V&V" link to read the Verification and Validation report.
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Click on the "Images" link to view and download preview images. Use the "Image types" subnavigation to cycle through available images.
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Use the "Back to Search Results" button to return to the previous page, allowing you to browse other observations.
When you are ready to download the dataset, make sure the ObsID(s) are you interested in are checked off in the search results page. By default, both the primary and secondary products (Figure 3) in ChaSeR. Uncheck either option if you don't wish to download both. Users can also request a custom package that may include level 0 and level 1.5 data products not previously accessible via this interface.
Figure 3: ChaSeR package selection
![[Thumbnail image: Both the primary and secondary package options are checked by default.]](webpkg.png)
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Figure 3: ChaSeR package selection
ChaSeR now allows you to select only certain files with the Custom Package option.
The selections are submitted using the "Add to Retrieval List" button. Proceed to the next step.
3. Retrieve
Use the "Browse Products" button to view the observations and data products submitted for selection (Figure 4). At the bottom of the list, the total number of files and combined filesize is listed: "Total: 28 files, 124,033,470 bytes uncompressed. (Note: Downloaded data will be compressed to about 50-70% of this size.) ".
Figure 4: ChaSeR retrieval list
![[Thumbnail image: The retrieval list shows which files will be downloaded.]](webretlist.png)
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Figure 4: ChaSeR retrieval list
There are 35 files in the primary and secondary product packages for this observation.
Use the "Retrieval List" link in the upper right to go back to the Retrieval List, then click the "Retrieve Products" button to start the retrieval process (Figure 5).
The files are compiled into a tarred package which is placed onto the archive web server (cdaftp.harvard.edu). If you provide your email address, you will receive an email when the tarfile is ready for download:
To: me@awesome.edu Date: Thu, 04 Apr 2013 14:39:46 -0400 Subject: Chandra Data Notification Your Chandra data are ready for retrieval at: https://cdaftp.cfa.harvard.edu/pub/stage/HNFIx8rD Files: 90M 2021-01-26 12:34:27 -0500 package_13275_210126123414.tar
Figure 5: Retrieval Results screen
![[Thumbnail image: The future location of the tarfile is listed, as well as a field for supplying your email address.]](webdownload.png)
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Figure 5: Retrieval Results screen
Make note of the URL location of the tarfile, or enter your email address to have it sent to you.
Next, follow the instructions in the URL and Unpack the Data section.
Chandra Footprint Service
The Chandra Fooprint Service lets you search for publically-available observations, showing you the "footprint" of each matching observation (that is, the area on the sky actually observered by Chandra). It is based on the interface used by the Hubble Legacy Archive. As shown below, search results can be browsed and filtered before choosing what observations you want to download.
Searching
Figure Figure 6 shows the start page of the search. In this example we have entered the object name G21.5-0.9 into the search box, but positions (RA/Dec only) can be used instead. The search defaults to a radius of 0.2 degrees, but this can be changed by appending r=0.5d to the end of the search string (change the value to suit your needs).
Figure 6: Starting a search for G21.5-0.9 with the Chandra Footprint Service
![[Thumbnail image: The text "G21.5-0.9" has been entered into the search box.]](footprint.start.png)
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Figure 6: Starting a search for G21.5-0.9 with the Chandra Footprint Service
The search box (highlighted by the red oval) can be used to enter a coordinate or name; here we use the name G21.5-0.9 and use the default search radius (of 0.2 degrees). The Help button can be used to find out more information on the supported formats for searching (as well as other parts of the interface).
To start the search either hit return when focus is in the search box, or select the search button. The page will reload with the results of the search (it may take some time, particularly if using a position with many matching results, as used in the example), resulting in a page like Figure 7.
Figure 7: The result of the search for G21.5-0.9 with the Chandra Footprint Service
![[Thumbnail image: The page now shows a DSS image with overlays for the observations and a table listing the matching observations.]](footprint.results.png)
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Figure 7: The result of the search for G21.5-0.9 with the Chandra Footprint Service
The first part of the results is a Digitized Sky Survey image of the area overlain with the field of views of the matching observations. A circle is also drawn, indicating the search radius, but in this case you can not see it because of all the observations!
The colors of the observation outlines indicate the particular instrument used for that observation, as shown on the left of the page (as highlighted by the red oval). The buttons allow you to turn off or on the display for each instrument.
Below the image is a table listing all the observations. In the screen shot shown here only the first two rows can be seen (and not all the columns), but if you were to scroll the page down you could see the first 20 rows. The number of rows in the table can be changed with the button/menu item shown just below the image.
A quick look at the observational data is possible via the "Preview Images" tab, as shown in Figure 8.
Figure 8: A quick look at the data
![[Thumbnail image: A page "quick-look" images for each observation is available.]](footprint.images.png)
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Figure 8: A quick look at the data
Selecting the Preview Images/Download Data tab - highlighted by the red rectangle - shows the "quick look" images for each observation.
Narrowing down your search
For most searches you are unlikely to have quite as many matches as the search shown here (this target is used to calibrate the instruments on Chandra, so has been observed many times), but you may still want to narrow down the results.
First we start by turning off the display for all but the HRC-S detector, leaving only the pink outlines. Clicking on one of the outlines will select it (and in fact any other observation that covers that point on the sky); the selected observations are drawn in a yellow outline and are highlighted with a green background in the table. An example is shown in Figure 9.
Figure 9: Showing just the HRC-S observations
![[Thumbnail image: By de-selecting the ACIS-I, ACIS-S, and HRC-I observations only the pink outlines of the HRC-S observations are shown.]](footprint.select.hrcs.png)
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Figure 9: Showing just the HRC-S observations
Clicking on a point in the image will select all those observations shown in the window - so in this case HRC-S ones only - that cover the point. In this case a point was chosen that corresponded to some ot the observations shown in the table; these are shown by the rows with a green background. Note that the table has not been filtered to show only HRC-S observations.
Multiple points can be selected; this will add to the set of selected observations, if there are any new ones to be added. Individual observations can also be selected by clicking on their row in the table.
The Reset Selection box - highlighted in Figure 9 by the red rectangle - will remove all the filters and selections, returning the display to the same as in Figure 7. The results can also be filtered by entering values into the text boxes below the column headers of the table; these are the blue boxes below the "ObsId", "Target", "Observation Date", ... entries in the table. In Figure 10 we show how to filter the ObsId column to show just those values between 1800 and 1900.
Figure 10: Filtering the results with the Chandra Footprint Service
![[Thumbnail image: Only a subset of results is now shown.]](footprint.filter.png)
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Figure 10: Filtering the results with the Chandra Footprint Service
After entering 1800..1900 into the text box below the ObsId header, the Apply Filter box/button will apply the filter (the red rectangles highlight both areas of the screen). For this example the filter restricts the results to 6 entries. The 1843 line has been selected, so it is shown as the yellow outline in the figure and with a green background in the table.
The Clear Filter button is used to remove any filters you have applied. Simple numeric and string filters are supported, as described in the help on filtering.
Clicking on the ObsId link for an individual observation will display the observation information collected by the archive in a separate window. An example is shown in Figure 11.
Figure 11: The information for ObsId 1843
![[Thumbnail image: A page of information about ObsId 1843, including links to further information.]](footprint.obsid.png)
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Figure 11: The information for ObsId 1843
Selecting the 1843 link in the table takes us to a new page containing detailed information about this observation. This is the same information as available from ChaSeR.
Downloading data
Once you have selected the observations you are interested in - that is, selected them so that they have a green background in the table - then the Download Selected ObsIDs button above the table will instruct the archive to create a tar file of the observations, and create a new window containing the name of the file, and its location at the Chandra download site. An example is shown below:
File(s) package_14398_210126123853.tar will be available at https://cdaftp.cfa.harvard.edu/pub/stage/flHhH0sl
This is similar to ChaSeR, so you can follow the same instructions for retrieving the data, except that there is no clickable link, so you have to either copy and paste the the link into your address bar or use wget (or curl).
Note that this is only a brief introduction to the Footprint Server, and has not discussed more complex capabilities, such as altering the columns displayed, or the IVOA Simple Image Access (SIA) interface. Note that the find_chandra_obsid script takes advantage of the SIA interface to allow you to search and download directly from the command line.
Chaser downloadable application(retired)
A downloadable Chaser Java application once existed but has been discontinued. Users can use ChaSeR to retrieve all the same data products as well as batch searches.
URL and Unpack the Data
The download_chandra_obsid and find_chandra_obsid scripts download the unpack the data into the current working directory. If you used ChaSeR or the footprint service you need to get the tarfile from the Archive HTTP server and unpack it.
In this example, we use the name of the tarfile created by ChaSeR: https://cdaftp.cfa.harvard.edu/pub/stage/flHhH0sl/package_14398_210126123853.tar. The name and location of your tarfile will be different.
There are several options for downloading the tarfile:
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Use wget or curl from the command line:
unix% wget https://cdaftp.cfa.harvard.edu/pub/stage/flHhH0sl/package_14398_210126123853.tar --2013-04-04 14:45:17-- https://cdaftp.cfa.harvard.edu/pub/stage/flHhH0sl/package_14398_210126123853.tar => `package_27906_130404143929.tar' Resolving cda.cfa.harvard.edu... 131.142.198.68 Connecting to cda.cfa.harvard.edu|131.142.198.68|:21... connected. Logging in as anonymous ... Logged in! ==> SYST ... done. ==> PWD ... done. ==> TYPE I ... done. ==> CWD /pub/stage/RYayl7LI ... done. ==> SIZE package_27906_130404143929.tar ... 84613120 ==> PASV ... done. ==> RETR package_27906_130404143929.tar ... done. Length: 84613120 (81M) 100%[======================================>] 84,613,120 66.9M/s in 1.2s 2013-04-04 14:45:20 (66.9 MB/s) - `package_27906_130404143929.tar' saved [84613120]unix% curl -o package_165370_230616113126.tar https://cdaftp.cfa.harvard.edu/pub/stage/ggIxbNra/package_165370_230616113126.tar % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 79.6M 100 79.6M 0 0 13.6M 0 0:00:05 0:00:05 --:--:-- 14.2M
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Open the URL in your web browser and use the "Save Link As..." (or similar) menu option to save the tarfile.
Once you have downloaded the file, use tar to extract its contents:
unix% tar xvf package_27906_130404143929.tar 1843/00README 1843/axaff01843N003_VV001_vv2.pdf 1843/oif.fits 1843/primary/acisf01843N004_cntr_img2.fits.gz 1843/primary/acisf01843N004_cntr_img2.jpg 1843/primary/acisf01843N004_evt2.fits.gz 1843/primary/acisf01843N004_full_img2.fits.gz 1843/primary/acisf01843N004_full_img2.jpg 1843/primary/acisf01843_000N004_bpix1.fits.gz 1843/primary/acisf01843_000N004_fov1.fits.gz 1843/primary/orbitf084197100N001_eph1.fits.gz 1843/primary/pcadf01843_000N001_asol1.fits.gz 1843/secondary/acisf01843_000N004_evt1.fits.gz 1843/secondary/acisf01843_000N004_flt1.fits.gz 1843/secondary/acisf01843_000N004_msk1.fits.gz 1843/secondary/acisf01843_000N004_mtl1.fits.gz 1843/secondary/acisf01843_000N004_stat1.fits.gz 1843/secondary/acisf084271178N004_0_bias0.fits.gz 1843/secondary/acisf084271178N004_1_bias0.fits.gz 1843/secondary/acisf084271178N004_2_bias0.fits.gz 1843/secondary/acisf084271178N004_3_bias0.fits.gz 1843/secondary/acisf084271178N004_4_bias0.fits.gz 1843/secondary/acisf084271178N004_5_bias0.fits.gz 1843/secondary/acisf084272477N004_pbk0.fits.gz 1843/secondary/aspect/pcadf084265646N004_osol1.fits.gz 1843/secondary/aspect/pcadf084271087N004_aqual1.fits.gz 1843/secondary/aspect/pcadf084272206N004_osol1.fits.gz 1843/secondary/aspect/pcadf084278602N004_osol1.fits.gz 1843/secondary/axaff01843N003_VV001_vvref2.pdf.gz 1843/secondary/ephem/anglesf01843_000N004_eph1.fits.gz 1843/secondary/ephem/lunarf084197100N001_eph1.fits.gz 1843/secondary/ephem/solarf084197100N001_eph1.fits.gz unix% ls 1843 package_27906_130404143929.tar
If you downloaded data from multiple ObsIds, a directory will be created for each of them.
The directory looks like:
unix% cd 1843 unix% ls -1 * -rw-rw-r-- 1 user group 10142 Jan 13 09:35 00README -rw-rw-r-- 1 user group 43076 Jan 13 09:35 axaff01843N003_VV001_vv2.pdf -rw-rw-r-- 1 user group 20160 Jan 13 09:35 oif.fits primary: total 21316 -rw-rw-r-- 1 user group 171766 Jan 13 09:35 acisf01843N004_cntr_img2.fits.gz -rw-rw-r-- 1 user group 853266 Jan 13 09:35 acisf01843N004_cntr_img2.jpg -rw-rw-r-- 1 user group 18069201 Jan 13 09:35 acisf01843N004_evt2.fits.gz -rw-rw-r-- 1 user group 63686 Jan 13 09:35 acisf01843N004_full_img2.fits.gz -rw-rw-r-- 1 user group 87510 Jan 13 09:35 acisf01843N004_full_img2.jpg -rw-rw-r-- 1 user group 18429 Jan 13 09:35 acisf01843_000N004_bpix1.fits.gz -rw-rw-r-- 1 user group 8610 Jan 13 09:35 acisf01843_000N004_fov1.fits.gz -rw-rw-r-- 1 user group 287913 Jan 13 09:35 orbitf084197100N001_eph1.fits.gz -rw-rw-r-- 1 user group 2136923 Jan 13 09:35 pcadf01843_000N001_asol1.fits.gz secondary: total 58868 -rw-rw-r-- 1 user group 36932603 Jan 13 09:35 acisf01843_000N004_evt1.fits.gz -rw-rw-r-- 1 user group 6551 Jan 13 09:35 acisf01843_000N004_flt1.fits.gz -rw-rw-r-- 1 user group 5161 Jan 13 09:35 acisf01843_000N004_msk1.fits.gz -rw-rw-r-- 1 user group 350429 Jan 13 09:35 acisf01843_000N004_mtl1.fits.gz -rw-rw-r-- 1 user group 298194 Jan 13 09:35 acisf01843_000N004_stat1.fits.gz -rw-rw-r-- 1 user group 436338 Jan 13 09:35 acisf084271178N004_0_bias0.fits.gz -rw-rw-r-- 1 user group 507553 Jan 13 09:35 acisf084271178N004_1_bias0.fits.gz -rw-rw-r-- 1 user group 440374 Jan 13 09:35 acisf084271178N004_2_bias0.fits.gz -rw-rw-r-- 1 user group 434442 Jan 13 09:35 acisf084271178N004_3_bias0.fits.gz -rw-rw-r-- 1 user group 437569 Jan 13 09:35 acisf084271178N004_4_bias0.fits.gz -rw-rw-r-- 1 user group 437043 Jan 13 09:35 acisf084271178N004_5_bias0.fits.gz -rw-rw-r-- 1 user group 4011 Jan 13 09:35 acisf084272477N004_pbk0.fits.gz drwxrwsr-x 2 user group 4096 Jan 13 09:35 aspect -rw-rw-r-- 1 user group 19696806 Jan 13 09:35 axaff01843N003_VV001_vvref2.pdf.gz drwxrwsr-x 2 user group 4096 Jan 13 09:35 ephem
The data files are now ready to be used in CIAO. For a description of the files, read the Introduction to the Data Products thread.
It is strongly suggested that you look at the V&V report for each observation; these are the <obsid>/axaf*_vv2.pdf files. Any know anomolies or irregularities in the data will be noted here that could affect the results.
History
| 03 Jan 2005 | reviewed for CIAO 3.2: no changes |
| 01 Dec 2005 | reviewed for CIAO 3.3: no changes |
| 01 Dec 2006 | reviewed for CIAO 3.4: no changes |
| 09 Jan 2007 | updated for CIAO 4.0: filenames updated since ObsID 1843 went through Repro III |
| 09 Jun 2008 | updated image display to place figures inline with text |
| 29 Sep 2008 | corrected link for downloading Chaser |
| 30 Dec 2008 | reviewed for CIAO 4.1: no changes |
| 25 Jan 2010 | reviewed for CIAO 4.2: no changes |
| 09 Nov 2010 | the download_chandra_obsid script is a quick and easy method of download data files. |
| 10 Jan 2011 | updated for CIAO 4.3: added more information on using the download_chandra_obsid script |
| 09 Jan 2012 | reviewed for CIAO 4.4: expanded information on using ChaSeR |
| 16 Feb 2012 | added a section on using the find_chandra_obsid script |
| 03 Dec 2012 | Review for CIAO 4.5; no changes. |
| 04 Apr 2013 | ChaSer is retired. WebChaser now supports individual data product downloads and the ability to upload a list of search criteria. |
| 28 May 2013 | Added a new section, The Chandra Footprint Service. |
| 26 Jul 2013 | Added a see also to the Chandra Source Catalog scripts. |
| 25 Nov 2013 | Review for CIAO 4.6. Updated formatting to draw attention to the need to reprocess and to review the V&V reports. |
| 16 Dec 2014 | Reviewed for CIAO 4.7. Added a note about find_chandra_obsid update to allow searching by OBS_ID. |
| 14 Dec 2015 | Reviewed for CIAO 4.8. Minor updates only. |
| 21 Jun 2016 | Updated for chaser rebranding and new screen shots. |
| 29 Dec 2016 | Review for CIAO4.9. Minor updates to footprint service outputs. |
| 16 May 2017 | Updated to use ftp://cda.cfa.harvard.edu instead of ftp://cdaftp.cfa.harvard.edu. |
| 26 Jan 2021 | Updated to use https://cxc.cfa.harvard.edu/cdaftp |
| 13 Jan 2022 | Reviewed for CIAO 4.14. Updated for Repro-5. |
| 30 Jun 2022 | Update some broken links. |