Chandra X-Ray Observatory
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Last modified: 16 May 2017

URL: http://cxc.harvard.edu/ciao/threads/archivedownload/

How to download Chandra Data from the Archive

CIAO 4.9 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: 16 May 2017 - Updated to use ftp://cda.cfa.harvard.edu instead of ftp://cdaftp.cfa.harvard.edu.


Contents


What data files do I need for my analysis?

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]
Always reprocess

The CXC strong 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.

If you are unsure what types of analysis you will be doing, downloading both the primary and secondary data packages ensure that you will have any file you might need.


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 81 Mb.

  Type     Format      Size  0........H.........1  Download Time Average Rate
  ---------------------------------------------------------------------------
  readme   ascii      11 Kb  ####################          < 1 s  438.5 kb/s
  oif      fits       23 Kb  ####################          < 1 s  921.3 kb/s
  vv       pdf        40 Kb  ####################          < 1 s  1103.2 kb/s
  cntr_img fits      237 Kb  ####################          < 1 s  4819.2 kb/s
  cntr_img jpg       925 Kb  ####################          < 1 s  12912.1 kb/s
  evt2     fits       17 Mb  ####################          < 1 s  48197.9 kb/s
  full_img fits       80 Kb  ####################          < 1 s  1469.4 kb/s
  full_img jpg        82 Kb  ####################          < 1 s  2687.9 kb/s
  bpix     fits       13 Kb  ####################          < 1 s  713.8 kb/s
  fov      fits        6 Kb  ####################          < 1 s  517.3 kb/s
  eph1     fits      281 Kb  ####################          < 1 s  4758.6 kb/s
  asol     fits        2 Mb  ####################          < 1 s  23733.1 kb/s
  evt1     fits       35 Mb  ####################          < 1 s  70499.1 kb/s
  flt      fits        7 Kb  ####################          < 1 s  89.0 kb/s
  msk      fits        5 Kb  ####################          < 1 s  248.3 kb/s
  mtl      fits      344 Kb  ####################          < 1 s  7074.4 kb/s
  stat     fits      290 Kb  ####################          < 1 s  9425.3 kb/s
  bias     fits      426 Kb  ####################          < 1 s  7242.6 kb/s
  bias     fits      494 Kb  ####################          < 1 s  8639.9 kb/s
  bias     fits      430 Kb  ####################          < 1 s  9533.6 kb/s
  bias     fits      423 Kb  ####################          < 1 s  7373.4 kb/s
  bias     fits      427 Kb  ####################          < 1 s  9268.9 kb/s
  bias     fits      427 Kb  ####################          < 1 s  6963.3 kb/s
  pbk      fits        4 Kb  ####################          < 1 s  591.5 kb/s
  vv       pdf        19 Mb  ####################          < 1 s  58441.4 kb/s
  eph1     fits        6 Kb  ####################          < 1 s  217.9 kb/s
  eph1     fits      274 Kb  ####################          < 1 s  5887.0 kb/s
  eph1     fits      258 Kb  ####################          < 1 s  6255.4 kb/s
  osol     fits      353 Kb  ####################          < 1 s  7858.5 kb/s
  aqual    fits      148 Kb  ####################          < 1 s  4554.0 kb/s
  osol     fits      343 Kb  ####################          < 1 s  9073.4 kb/s
  osol     fits      354 Kb  ####################          < 1 s  11692.4 kb/s

      Total download size for ObsId 1843 = 81 Mb
      Total download time for ObsId 1843 = 2 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 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:

  1. 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]"
    ...
    
  2. 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                 14.0
    

    The 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 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.

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.

[Thumbnail image: The Search Results page lists all results of the search for ACIS-I observations of G21.5-0.9]

[Version: full-size]

[Print media version: The Search Results page lists all results of the search for ACIS-I observations of G21.5-0.9]

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:

  • Use the "Details" link to display specifics about the observation, e.g. general observation parameters, ACIS-specific parameters, and any observation contraints.

  • Use the "V&V" link to read the Verification and Validation report.

  • Click on the "Images" link to view and download preview images. Use the "Image types" subnavigation to cycle through available images.

  • 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.

[Thumbnail image: Both the primary and secondary package options are checked by default.]

[Version: full-size]

[Print media version: Both the primary and secondary package options are checked by default.]

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.) ".

[Thumbnail image: The retrieval list shows which files will be downloaded.]

[Version: full-size]

[Print media version: The retrieval list shows which files will be downloaded.]

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 anonymous FTP server (cda.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 to be retrieved via anonymous ftp
at cda.cfa.harvard.edu in the directory /pub/stage/RYayl7LI.

Files:

total 82800
-r--r--r-- 1 arcpub2 dbm_dev 84613120 Apr  4 14:39 package_27906_130404143929.tar
[Thumbnail image: The future location of the tarfile is listed, as well as a field for supplying your email address.]

[Version: full-size]

[Print media version: The future location of the tarfile is listed, as well as a field for supplying your email address.]

Figure 5: Retrieval Results screen

Make note of the FTP location of the tarfile, or enter your email address to have it sent to you.

Next, follow the instructions in the FTP and Unpack the Data section.


Chandra Footprint Service

The Chandra Footprint 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).

[Thumbnail image: The text "G21.5-0.9" has been entered into the search box.]

[Version: full-size]

[Print media version: The text "G21.5-0.9" has been entered into the search box.]

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.

[Thumbnail image: The page now shows a DSS image with overlays for the observations and a table listing the matching observations.]

[Version: full-size]

[Print media version: The page now shows a DSS image with overlays for the observations and a table listing the matching observations.]

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.

[Thumbnail image: A page "quick-look" images for each observation is available.]

[Version: full-size]

[Print media version: A page "quick-look" images for each observation is available.]

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.

[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.]

[Version: full-size]

[Print media version: By de-selecting the ACIS-I, ACIS-S, and HRC-I observations only the pink outlines of the HRC-S observations are shown.]

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.

[Thumbnail image: Only a subset of results is now shown.]

[Version: full-size]

[Print media version: Only a subset of results is now shown.]

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.

[Thumbnail image: A page of information about ObsId 1843, including links to further information.]

[Version: full-size]

[Print media version: A page of information about ObsId 1843, including links to further information.]

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 FTP site. An example is shown below:

File(s) package_5832_130523142917.tar will be available at ftp://cda.cfa.harvard.edu/pub/stage/2dRTwkc5

This is similar to ChaSeR, so you can follow the same instructions for retrieving the data, except that there is no link to click on from within your browser, so you have to either use wget (or curl), or log in to the FTP server directly.

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 pplication(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.


FTP 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 anonymous FTP server and unpack it.

In this example, we use the name of the tarfile created by ChaSeR: . The name and location of your tarfile will be different.

There are several options for downloading the tarfile:

  1. Use wget or curl from the command line:

    unix% wget ftp://cda.cfa.harvard.edu/pub/stage/RYayl7LI/package_27906_130404143929.tar
    --2013-04-04 14:45:17--  ftp://cda.cfa.harvard.edu/pub/stage/RYayl7LI/package_27906_130404143929.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]
    
  2. Open the ftp link in your web browser and use the "Save Link As..." (or similar) menu option to save the tarfile. Note that this is only possible for ChaSeR since the footprint service does not provide a link to follow.

  3. Log in to the anonymous FTP server and get the file:

    unix% ftp cda.harvard.edu
    % ftp cda.harvard.edu
    Connected to cda.harvard.edu (131.142.198.68).
    220-Warning - Computer Use Policy in Effect
     
     Unauthorized access and use of this computer is a criminal violation
     of the Computer Fraud and Abuse Act (18 U.S.C. Sec. 1030). The
     responsibilities of all users of this system are described in
     Smithsonian Directive 931 (http://www.cfa.harvard.edu/do/sd931.pdf).
     Use of this computer and any other CfA IT assets implies an acceptance
     of the terms and conditions stated in SD 931.  Any violation of these
     policies should be reported to syshelp@head.cfa.harvard.edu
     -----------------------------------------------------------------------
     
    220 Chandra Public FTP Archive cda.cfa.harvard.edu
    Name (cda.harvard.edu:user): ftp
    331 Anonymous login ok, send your complete email address as your password
    Password: me@awesome.edu
    230-                 Welcome to the Chandra Data Archive
     
                     This server is cda.cfa.harvard.edu 
     
     If your FTP client crashes or hangs shortly after login please try
     using a dash (-) as the first character of your password.  This will
     turn off the informational messages that may be confusing your FTP
     client.
     
     Publicly available files are in /pub
     
     Problems with this ftp site?  Contact arcops@head.cfa.harvard.edu
     
       +---------------------------------------------------------------+
       |                                                               |
       |    This ftp site is the anonymous ftp version of the CDA.     |
       |    It contains all primary and secondary products of all      |
       |    public Chandra observations and is being kept up-to-date   |
       |    in real time. That means that observations that are        |
       |    released to the public are available from this ftp archive |
       |    almost immediately and that old data versions are replaced |
       |    by new, reprocessed ones as soon as they are released.     |
       |                                                               |
       |    For further information, please consult the file 00README. |
       |                                                               |
       |    Mirror site opportunities: see the file 00README.          |
       |                                                               |
       +---------------------------------------------------------------+
     
     
         +---------------------------------------------------------+
         |                                                         |
         |    Data packages created by WebChaSeR can be found      | 
         |    here in the directory provided by these archival     |
         |    search and retrieval tools.                          |
         |                                                         |
         |    PLEASE NOTE:                                         |
         |                                                         |
         |    If the directory provided to you by WebChaSeR appears|
         |    to be empty, this is a sign that your tar file is    |
         |    not yet ready.  Please try again in a little while.  |
         |                                                         |
         +---------------------------------------------------------+
    230 Anonymous access granted, restrictions apply
    Remote system type is UNIX.
    Using binary mode to transfer files.
    ftp> cd /pub/stage/RYayl7LI
    250 CWD command successful
    ftp> binary
    200 Type set to I
    ftp> get package_27906_130404143929.tar
    local: package_27906_130404143929.tar remote: package_27906_130404143929.tar
    227 Entering Passive Mode (131,142,198,68,223,65).
    150 Opening BINARY mode data connection for package_27906_130404143929.tar (84613120 bytes)
    226 Transfer complete
    84613120 bytes received in 2.57 secs (3.2e+04 Kbytes/sec)
    

Once you have downloaded the file, use tar to extract its contents:

unix% tar xvf package_27906_130404143929.tar 
1843/oif.fits
1843/primary/acisf01843N003_full_img2.jpg
1843/primary/acisf01843N003_cntr_img2.fits.gz
1843/primary/acisf01843N003_full_img2.fits.gz
1843/primary/acisf01843N003_evt2.fits.gz
1843/primary/pcadf084271087N003_asol1.fits.gz
1843/primary/acisf01843_000N003_bpix1.fits.gz
1843/primary/acisf01843_000N003_fov1.fits.gz
1843/primary/orbitf084197100N001_eph1.fits.gz
1843/primary/acisf01843N003_cntr_img2.jpg
1843/axaff01843N002_VV001_vv2.pdf
1843/secondary/aspect/pcadf084271087N003_aqual1.fits.gz
1843/secondary/aspect/pcadf084265646N003_osol1.fits.gz
1843/secondary/aspect/pcadf084272206N003_osol1.fits.gz
1843/secondary/aspect/pcadf084278602N003_osol1.fits.gz
1843/secondary/ephem/anglesf01843_000N003_eph1.fits.gz
1843/secondary/ephem/lunarf084197100N001_eph1.fits.gz
1843/secondary/ephem/solarf084197100N001_eph1.fits.gz
1843/secondary/acisf01843_000N003_stat1.fits.gz
1843/secondary/acisf01843_000N003_flt1.fits.gz
1843/secondary/acisf01843_000N003_msk1.fits.gz
1843/secondary/acisf01843_000N003_mtl1.fits.gz
1843/secondary/acisf01843_000N003_evt1.fits.gz
1843/secondary/acisf084271178N003_1_bias0.fits.gz
1843/secondary/acisf084271178N003_0_bias0.fits.gz
1843/secondary/acisf084271178N003_2_bias0.fits.gz
1843/secondary/acisf084271178N003_4_bias0.fits.gz
1843/secondary/acisf084271178N003_3_bias0.fits.gz
1843/secondary/acisf084271178N003_5_bias0.fits.gz
1843/secondary/acisf084272477N003_pbk0.fits.gz
1843/secondary/axaff01843N002_VV001_vvref2.pdf.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 *
-r--r--r-- 1 user group 40495 Sep  6  2012 axaff01843N002_VV001_vv2.pdf
-r--r--r-- 1 user group 23040 Sep  6  2012 oif.fits

primary:
total 21808
-r--r--r-- 1 user group   242483 Sep  3  2012 acisf01843N003_cntr_img2.fits.gz
-r--r--r-- 1 user group   947669 Sep  3  2012 acisf01843N003_cntr_img2.jpg
-r--r--r-- 1 user group 18075861 Sep  3  2012 acisf01843N003_evt2.fits.gz
-r--r--r-- 1 user group    82043 Sep  3  2012 acisf01843N003_full_img2.fits.gz
-r--r--r-- 1 user group    83881 Sep  3  2012 acisf01843N003_full_img2.jpg
-r--r--r-- 1 user group    13679 Sep  3  2012 acisf01843_000N003_bpix1.fits.gz
-r--r--r-- 1 user group     5924 Sep  3  2012 acisf01843_000N003_fov1.fits.gz
-r--r--r-- 1 user group   287913 Oct  2  2000 orbitf084197100N001_eph1.fits.gz
-r--r--r-- 1 user group  2497395 Sep  3  2012 pcadf084271087N003_asol1.fits.gz

secondary:
total 59272
-r--r--r-- 1 user group 36885019 Sep  3  2012 acisf01843_000N003_evt1.fits.gz
-r--r--r-- 1 user group     6949 Sep  3  2012 acisf01843_000N003_flt1.fits.gz
-r--r--r-- 1 user group     5467 Sep  3  2012 acisf01843_000N003_msk1.fits.gz
-r--r--r-- 1 user group   352300 Sep  3  2012 acisf01843_000N003_mtl1.fits.gz
-r--r--r-- 1 user group   297382 Sep  3  2012 acisf01843_000N003_stat1.fits.gz
-r--r--r-- 1 user group   436185 Sep  2  2012 acisf084271178N003_0_bias0.fits.gz
-r--r--r-- 1 user group   505974 Sep  2  2012 acisf084271178N003_1_bias0.fits.gz
-r--r--r-- 1 user group   440218 Sep  2  2012 acisf084271178N003_2_bias0.fits.gz
-r--r--r-- 1 user group   433301 Sep  2  2012 acisf084271178N003_3_bias0.fits.gz
-r--r--r-- 1 user group   437445 Sep  2  2012 acisf084271178N003_4_bias0.fits.gz
-r--r--r-- 1 user group   436956 Sep  2  2012 acisf084271178N003_5_bias0.fits.gz
-r--r--r-- 1 user group     4009 Sep  2  2012 acisf084272477N003_pbk0.fits.gz
drwxrwxr-x 2 user group     4096 Apr  4 14:49 aspect
-r--r--r-- 1 user group 20264414 Sep  6  2012 axaff01843N002_VV001_vvref2.pdf.gz
drwxrwxr-x 2 user group     4096 Apr  4 14:49 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.

[IMPORTANT]
V&V report

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.


Last modified: 16 May 2017
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