How to Download Chandra Data from the Archive

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.

Each of the threads also includes a list of the specific files needed to run it.

If you are unsure what analyses 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 67 Mb.

  Type     Format      Size  0........H.........1  Download Time Average Rate
  ---------------------------------------------------------------------------
  vv       pdf        78 Kb  ####################          < 1 s  1593.2 kb/s
  oif      fits       23 Kb  ####################          < 1 s  461.3 kb/s
  sum      html        2 Kb  ####################          < 1 s  32.2 kb/s
  sum      ps          2 Mb  ####################          < 1 s  10615.7 kb/s
  sum      html        4 Kb  ####################          < 1 s  84.5 kb/s
  sum      html        3 Kb  ####################          < 1 s  56.1 kb/s
  cntr_img fits      236 Kb  ####################          < 1 s  3225.8 kb/s
  cntr_img jpg       871 Kb  ####################          < 1 s  9827.2 kb/s
  evt2     fits       17 Mb  ####################            2 s  11355.7 kb/s
  full_img fits       80 Kb  ####################          < 1 s  1556.3 kb/s
  full_img jpg        77 Kb  ####################          < 1 s  1353.9 kb/s
  src2     fits        9 Kb  ####################          < 1 s  172.5 kb/s
  src_img  jpg        78 Kb  ####################          < 1 s  1544.3 kb/s
  bpix     fits       11 Kb  ####################          < 1 s  201.9 kb/s
  fov      fits        6 Kb  ####################          < 1 s  109.5 kb/s
  eph1     fits      281 Kb  ####################          < 1 s  5580.8 kb/s
  asol     fits        2 Mb  ####################          < 1 s  10743.0 kb/s
  aoff     fits     1005 Kb  ####################          < 1 s  9853.0 kb/s
  evt1     fits       35 Mb  ####################            3 s  11393.0 kb/s
  flt      fits        7 Kb  ####################          < 1 s  141.0 kb/s
  msk      fits        5 Kb  ####################          < 1 s  99.3 kb/s
  mtl      fits      344 Kb  ####################          < 1 s  7018.1 kb/s
  soff     fits        4 Kb  ####################          < 1 s  76.0 kb/s
  stat     fits      290 Kb  ####################          < 1 s  5755.9 kb/s
  bias     fits      426 Kb  ####################          < 1 s  8464.1 kb/s
  bias     fits      494 Kb  ####################          < 1 s  8866.2 kb/s
  bias     fits      430 Kb  ####################          < 1 s  8381.4 kb/s
  bias     fits      423 Kb  ####################          < 1 s  8611.5 kb/s
  bias     fits      427 Kb  ####################          < 1 s  8503.9 kb/s
  bias     fits      427 Kb  ####################          < 1 s  8425.0 kb/s
  pbk      fits        4 Kb  ####################          < 1 s  74.9 kb/s
  vv       pdf         2 Mb  ####################          < 1 s  10822.3 kb/s
  eph1     fits        6 Kb  ####################          < 1 s  127.7 kb/s
  eph1     fits      274 Kb  ####################          < 1 s  5156.1 kb/s
  eph1     fits      258 Kb  ####################          < 1 s  5195.1 kb/s
  osol     fits      351 Kb  ####################          < 1 s  6888.5 kb/s
  aqual    fits      148 Kb  ####################          < 1 s  2982.9 kb/s
  osol     fits      341 Kb  ####################          < 1 s  6967.2 kb/s
  osol     fits      356 Kb  ####################          < 1 s  6790.7 kb/s

      Total download size for ObsId 1843 = 67 Mb
      Total download time for ObsId 1843 = 7 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 G21.5-0.9
# find_chandra_obsid (15 February 2012): ERROR No position found matching the name 'G21.5-0.9'.
unix% find_chandra_obsid G21.5-09
# find_chandra_obsid (15 February 2012): ERROR No position found matching the name 'G21.5-09'.

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
   102
   unix% dmlist matches.txt"[sepn<1,inst=ACIS-I]" counts
   40
   unix% dmlist matches.txt"[sepn<1,inst=ACIS-I,time>10][cols obsid,time]" data,clean
   #  obsid                time
                   162.0                13.20
                  1233.0                14.20
                  5158.0                10.10
                  1552.0                10.40
   

   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.

Using WebChaSeR

WebChaSeR 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.

Unlike download_chandra_obsid, WebChaSeR doesn't allow you to select specific files for download. You can only select complete packages of primary and secondary products.

1. Browse

Chandra Archive data may be browsed using any of the fields in WebChaSeR, 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 WebChaSeR, change the Sort Order to "Observation ID".

Figure 1 shows the completed form.

Figure 1: The completed WebChaSeR form to search for ACIS-I observations of G21.5-0.9

[Version: full-size]

Figure 1: The completed WebChaSeR 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 WebChaSeR Search Results page

[Version: full-size]

Figure 2: The WebChaSeR Search Results page

Search results may be sorted by the "Order By..." menu.

The default number of rows returned in WebChaSeR is 50. If your search matches more than 50 observations, a message will be shown in the bottom left of the results page: 76 observations found, 50 displayed (where it says 36 observations found 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 WebChaSeR. Uncheck either option if you don't wish to download both.

Figure 3: WebChaSeR package selection

[Version: full-size]

Figure 3: WebChaSeR package selection

Unlike download_chandra_obsid, WebChaSeR doesn't allow you to select specific files for download. You can only select complete packages of primary and secondary products.

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: 35 files, 125,786,551 bytes uncompressed. (Note: Downloaded data will be compressed to about 50-70% of this size.) ".

Figure 4: WebChaSeR retrieval list

[Version: full-size]

Figure 4: WebChaSeR 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 (cdaftp.harvard.edu). If you provide your email address, you will receive an email when the tarfile is ready for download:

Subject: Chandra Data Notification
Date: Mon, 09 Jan 2012 12:22:11 -0500
From: cda@head.cfa.harvard.edu
To: you

Your Chandra data are ready to be retrieved via anonymous ftp
at cdaftp.cfa.harvard.edu in the directory /pub/stage/CSGwgNPJ.

Files:

total 69160
-r--r--r--   1 nobody   70676480 Jan  9 12:21 package_14140_120109122108.tar

Figure 5: Retrieval Results screen

[Version: full-size]

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.

Using ChaSeR

Before beginning, download and install the Java application.

Once installed, launch ChaSeR from the command line:

unix% chaser &

Figure 6 shows the GUI that will appear.

Figure 6: The ChaSeR GUI

[Version: full-size]

Figure 6: The ChaSeR GUI

The default settings of the ChaSeR GUI when it is launched are to search all instrument configurations for all types and categories of observations.

Using ChaSeR to obtain data is a simple four-step process:

1. Browse

Chandra Archive data may be browsed using any of the fields in the ChaSeR GUI, such as Instrument, Grating, ObsID, and Category. Since we are interested in an ACIS-I observation of G21.5-0.9, leave only the appropriate Instrument (ACIS-I) and Grating (NONE) options checked and enter the Target Name.

Figure 7 shows the completed form.

Figure 7: The complete form to search for ACIS-I observations of G21.5-0.9

[Version: full-size]

Figure 7: The complete form to search for ACIS-I observations of G21.5-0.9

Click the "Submit" button to enter the request.

---

2. Select

The Search Results window brings up all the observations that match our search criteria, as shown in Figure 8.

Figure 8: The Search Results window

[Version: full-size]

Figure 8: The Search Results window

Search results may be sorted by the "Order By..." menu.

The "Order By..." menu can be used to sort the results; here we have ordered them by "Observation ID."

Click on ObsID 1843 to highlight the row. After doing so one may:

• Use the "Detail" button to display specifics about the observation.

• Click on the "Images" button to see preview images.

• Write the table information to a file ("Save").

Now the desired data products may be selected for download using the "Select primary products", "Select secondary products", and "Select supporting products" buttons.

By default, all primary and secondary products are pre-selected. Files may be unchcekd if you are only interested in downloading specific files need for a thread. For help determing what those are, check the Standard Data Distribution Contents webpage. These tables list the file extensions (aka "Type") and the "Content"; the content keyword is how the products are labeled in the ChaSeR interface.

The selections are submitted using the "Add to retrieval list" button. You can then highlight a different observation and add the same (or different) data products to the cart for it. Once you have selected all the data you are interested in, proceed to the next step.

---

3. Retrieve

Click on "View retrieval list" to view the observations and data products submitted for selection (Figure 9).

Figure 9: The retrieval list

[Version: full-size]

Figure 9: The retrieval list

Since all the primary and secondary products were selected for retrieval, only the categories are listed. If specific files are chosen, they are listed individually.

One may see the list of data filenames and sizes (Figure 10) by clicking on the "Browse selected products" button.

Figure 10: Browse Results window

[Version: full-size]

Figure 10: Browse Results window

The total file size of the package is listed at the top of the screen. Use this information to make sure there is sufficient disk space to download and unpack the data.

The "Retrieve selected products" button is used to start the retrieval process. The files are compiled into a tarred package which is placed onto the anonymous FTP server (cda.harvard.edu) by default; the tarfile can also be saved directly to a local disk. When the download is complete, the ChaSeR window will look as shown in Figure 11. Note that the location of the logfile (chaser.log) and the FTP directory in which the tarfile was placed are given at the bottom of the GUI.

Figure 11: Completed download screen

[Version: full-size]

Figure 11: Completed download screen

When the download has completed, the location of the logfile (chaser.log) and the FTP directory in which the tarfile was placed are displayed at the bottom of the GUI.

The name and location of the tarfile is recorded in chaser.log, along with the ObsID that was downloaded:

unix% cat /export/chaser.log
[09/01/2008 14:55:46:310 EST]  Request retrieval of 1843
[09/01/2008 14:55:46:366 EST]  File(s) package_146_080109145545.tar.* will be available at cda.harvard.edu:/pub/srftp/I6bjzJSZ

When you are finished with ChaSeR, use the "Exit" button to close the GUI.

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

FTP and Unpack the Data

The download_chandra_obsid script downloads the files into the current working directory. If you used WebChaSeR or ChaSeR, you need to get the tarfile from Archive anonymous FTP server and unpacke it.

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

There are several options for downloading the tarfile:

1. Use wget from the command line:

   unix% wget ftp://cdaftp.cfa.harvard.edu/pub/stage/CSGwgNPJ/package_14140_120109122108.tar
   
   --2012-01-09 12:35:38--  ftp://cdaftp.cfa.harvard.edu/pub/stage/CSGwgNPJ/package_14140_120109122108.tar
              => `package_14140_120109122108.tar'
   Resolving cdaftp.cfa.harvard.edu... 131.142.198.68
   Connecting to cdaftp.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/CSGwgNPJ ... done.
   ==> SIZE package_14140_120109122108.tar ... 70676480
   ==> PASV ... done.    ==> RETR package_14140_120109122108.tar ... done.
   Length: 70676480 (67M)
   
   100%[======================================>] 70,676,480  11.2M/s   in 6.1s    
   
   2012-01-09 12:35:44 (11.0 MB/s) - `package_14140_120109122108.tar' saved [70676480]
   

2. Open the ftp link in your web browser and use the "Save Link As..." (or similar) menu option to save the tarfile.

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

   unix% ftp cdaftp.harvard.edu
   Connected to cdaftp.harvard.edu (131.142.198.68).
   220-            Welcome to the FTP server at the CXC Science Center
   220-
   220-                    This server is cdaftp1.cfa.harvard.edu
   220-
   220-
   220 cdaftp1 FTP server ready.
   Name (cda.harvard.edu:username): anonymous
   331 Guest login ok, send your complete e-mail address as password.
   Password:
   230-
   230-    Welcome to the FTP server at the CXC Science Center 
   230-
   230-            This server is cda.harvard.edu 
   230-
   230-If your FTP client crashes or hangs shortly after login please try
   230-using a dash (-) as the first character of your password.  This will
   230-turn off the informational messages that may be confusing your FTP
   230-client.
   230-
   230-Publicly available files are in /pub
   230-
   230-Problems with this ftp site?  Contact arcops@head.cfa.harvard.edu
   230-
   230-  +---------------------------------------------------------------+
   230-  |                                                               |
   230-  |    This ftp site is the anonymous ftp version of the CDA.     |
   230-  |    It contains all primary and secondary products of all      |
   230-  |    public Chandra observations and is being kept up-to-date   |
   230-  |    in real time. That means that observations that are        |
   230-  |    released to the public are available from this ftp archive |
   230-  |    almost immediately and that old data versions are replaced |
   230-  |    by new, reprocessed ones as soon as they are released.     |
   230-  |                                                               |
   230-  |    For further information, please consult the file 00README. |
   230-  |                                                               |
   230-  |    Mirror site opportunities: see the file 00README.          |
   230-  |                                                               |
   230-  +---------------------------------------------------------------+
   230-
   230-
   230-    +---------------------------------------------------------+
   230-    |                                                         |
   230-    |    Data packages created by WebChaSeR can be found      | 
   230-    |    here in the directory provided by these archival     |
   230-    |    search and retrieval tools.                          |
   230-    |                                                         |
   230-    |    PLEASE NOTE:                                         |
   230-    |                                                         |
   230-    |    If the directory provided to you by WebChaSeR appears|
   230-    |    to be empty, this is a sign that your tar file is    |
   230-    |    not yet ready.  Please try again in a little while.  |
   230-    |                                                         |
   230-    +---------------------------------------------------------+
   230-
   230-
   230 Guest login ok, access restrictions apply.
   Remote system type is UNIX.
   Using binary mode to transfer files.
   
   
   ftp> cd /pub/stage/CSGwgNPJ
   250 CWD command successful.
   
   ftp> get package_14140_120109122108.tar
   local: package_14140_120109122108.tar remote: package_14140_120109122108.tar
   227 Entering Passive Mode (131,142,198,68,251,17)
   150 Opening BINARY mode data connection for package_14140_120109122108.tar (70676480 bytes).
   226 Transfer complete.
   70676480 bytes received in 6.03 secs (1.1e+04 Kbytes/sec)
   
   ftp> exit
   221-You have transferred 70676480 bytes in 1 files.
   221-Total traffic for this session was 70679966 bytes in 2 transfers.
   221-Thank you for using the FTP service on cdaftp1.
   221 Goodbye.
   

Unpack the tarfile:

unix% tar xvf package_14140_120109122108.tar 
1843/oif.fits
1843/primary/acisf01843N002_1_sum2.html
1843/primary/acisf01843N002_1_sum2.ps
1843/primary/acisf01843N002_2_sum2.html
1843/primary/acisf01843N002_3_sum2.html
1843/primary/acisf01843N002_cntr_img2.fits.gz
1843/primary/acisf01843N002_cntr_img2.jpg
1843/primary/acisf01843N002_evt2.fits.gz
1843/primary/acisf01843N002_full_img2.fits.gz
1843/primary/acisf01843N002_full_img2.jpg
1843/primary/acisf01843N002_src2.fits.gz
1843/primary/acisf01843N002_src_img2.jpg
1843/primary/acisf01843_000N002_bpix1.fits.gz
1843/primary/acisf01843_000N002_fov1.fits.gz
1843/primary/orbitf084197100N001_eph1.fits.gz
1843/primary/pcadf084271087N002_asol1.fits.gz
1843/axaff01843N001_VV001_vv2.pdf
1843/secondary/aspect/pcadf084265646N001_osol1.fits.gz
1843/secondary/aspect/pcadf084271087N002_aqual1.fits.gz
1843/secondary/aspect/pcadf084272206N001_osol1.fits.gz
1843/secondary/aspect/pcadf084278602N001_osol1.fits.gz
1843/secondary/ephem/anglesf01843_000N002_eph1.fits.gz
1843/secondary/ephem/lunarf084197100N001_eph1.fits.gz
1843/secondary/ephem/solarf084197100N001_eph1.fits.gz
1843/secondary/acisf01843_000N002_aoff1.fits.gz
1843/secondary/acisf01843_000N002_evt1.fits.gz
1843/secondary/acisf01843_000N002_flt1.fits.gz
1843/secondary/acisf01843_000N002_msk1.fits.gz
1843/secondary/acisf01843_000N002_mtl1.fits.gz
1843/secondary/acisf01843_000N002_soff1.fits.gz
1843/secondary/acisf01843_000N002_stat1.fits.gz
1843/secondary/acisf084271178N002_0_bias0.fits.gz
1843/secondary/acisf084271178N002_1_bias0.fits.gz
1843/secondary/acisf084271178N002_2_bias0.fits.gz
1843/secondary/acisf084271178N002_3_bias0.fits.gz
1843/secondary/acisf084271178N002_4_bias0.fits.gz
1843/secondary/acisf084271178N002_5_bias0.fits.gz
1843/secondary/acisf084272477N002_pbk0.fits.gz
1843/secondary/axaff01843N001_VV001_vvref2.pdf.gz

unix% ls
1843/
package_14140_120109122108.tar 

unix% rm package_14140_120109122108.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 *
axaff01843N001_VV001_vv2.pdf
oif.fits

primary:
acisf01843_000N002_bpix1.fits.gz
acisf01843_000N002_fov1.fits.gz
acisf01843N002_1_sum2.html
acisf01843N002_1_sum2.ps
acisf01843N002_2_sum2.html
acisf01843N002_3_sum2.html
acisf01843N002_cntr_img2.fits.gz
acisf01843N002_cntr_img2.jpg
acisf01843N002_evt2.fits.gz
acisf01843N002_full_img2.fits.gz
acisf01843N002_full_img2.jpg
acisf01843N002_src2.fits.gz
acisf01843N002_src_img2.jpg
orbitf084197100N001_eph1.fits.gz
pcadf084271087N002_asol1.fits.gz

secondary:
acisf01843_000N002_aoff1.fits.gz
acisf01843_000N002_evt1.fits.gz
acisf01843_000N002_flt1.fits.gz
acisf01843_000N002_msk1.fits.gz
acisf01843_000N002_mtl1.fits.gz
acisf01843_000N002_soff1.fits.gz
acisf01843_000N002_stat1.fits.gz
acisf084271178N002_0_bias0.fits.gz
acisf084271178N002_1_bias0.fits.gz
acisf084271178N002_2_bias0.fits.gz
acisf084271178N002_3_bias0.fits.gz
acisf084271178N002_4_bias0.fits.gz
acisf084271178N002_5_bias0.fits.gz
acisf084272477N002_pbk0.fits.gz
aspect/
axaff01843N001_VV001_vvref2.pdf.gz
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.