• See also the ChaSeR reference (less verbose)
• ChaSeR FAQ
• Feedback, known bugs, and current limitations
• Download and installation
• Engineering Request data

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Introduction

To run ChaSeR:

	chaser
  

NOTE: If you are not on your own machine and are using ssh to remotely log into another machine to run ChaSeR, you must explicitly set the DISPLAY environment variable, as in:

	setenv DISPLAY yourmachine:0.0
      

In general, we advise against running Java applications (this is not peculiar to ChaSeR) remotely.

The CDA Search and Retrieval interface allows Chandra users to browse the archive and retrieve any data - public or proprietary - provided that they are authorized to receive the products. No specific privileges are required for:

• browsing
• retrieving any products from observations that are publicly released
• retrieving non-proprietary products from proprietary observations (e.g., aspect or engineering data)

For the retrieval of proprietary data products one needs to log in to a privileged account - either a PI account (good for products from observations for which that person is PI), or a proposal account (good for products from observations under a specific proposal). Account names and passwords will soon be distributed to PIs who will be responsible for passing that information on to collaborators as they see fit. ChaSeR: does allow users to change passwords. If you would like the receive information on your accounts now, or if you need additional information, please E-mail arcops.

Searching in, and retrieving data from, the CDA is a four-step process, very much like shopping on the web:

1. Browse for products
2. Select products and put them in your shopping cart
3. Check the contents of your shopping cart
4. Place your order

Steps 1, 2, and 3 can be repeated multiple times before step 4 is executed.

The S&R application has three interactive screens:

• Observation Search, for step 1
• Search Results, for step 2
• Retrieval List (Shopping Cart), for steps 3 and 4

For a graphical representation of the functional flow (PDF format), click here.

Engineering Request Data

ChaSeR cannot access data products associated with Engineering Requests (ER). For access to ER data use RetrievER. Note that ERs do not contain any data that are of scientific interest and users may safely ignore them.

Observation Search

The first screen allows the user to specify constraints in order to find observations that match what (s)he wants. Most of the fields are self-explanatory and their use becomes clear when clicked on. For instance, in coordinates one can specify a rectangular region to be searched or a cone; clicking on the coordinate input fields will bring up a pop-up window that gives the user that choice.

Source names may be converted to celestial coordinates through the SIMBAD name resolver.

Names or coordinates may be read from an ASCII file, instead of being entered on the form, allowing multiple searches to be executed in one query. When doing so, the other search constraints remain in effect.

ChaSeR is very finicky about the format of the input file The input file needs to have on its first line the name(s) of the field(s) that are provided in the input file, separated by a tab if more than one. Valid fields are:

• Target Name; or
• RA and DEC; or
• LONG and LAT; or
• L2 and B2

There can be no leading or trailing blanks. Make sure that this specification agrees with what is specified on ChaSeR's screen. The search values are given, each set on a separate line, and again separated by a tab; the coordinate format should agree with what is specified on the screen and there should not be any leading or trailing blanks. The only whitespace allowed are blanks within a single value field (e.g., a target name or a sexagesimal string) and a single tab separating two fields on the same line. Make sure the Search Radius is set.

For example:

	L2	B2
	123.4	12.3
	56.78	-45.678
  

or:

	RA	DEC
	08 13 36.00	+12 18 00.00
	03 47 07.20	-45 40 40.80
  

or:

	Target Name
	M81
	2MASX J06094582-21402
	AM 0702-601
	ARP 148
  

The normal output of the Observation Search is the Search Results screen. However, the user may request to have the search results sent to a file.

Press Submit to execute the search.

Search Results

The results of the search are presented in tabular form. All observations with status Archived have been publicly released.

Observations may be selected by clicking on them. Control-clicking selects multiple entries. A contiguous range is selected by clicking on the first and Shift-clicking on the last. Details and summary images of selected observations may be displayed by clicking on the Detail and Images buttons, respectively; summary images can only be displayed for public observations (status archived).

The user may select certain data product types for selected observations and add these to the Retrieve List. When the Add to Retrieval List button is pressed the selected products will be added to the shopping cart for the selected observations. This action may be repeated as often as necessary - with the same or with different observations, from the same observation search or from a new observation search. The default selection is all Primary and Secondary products.

The standard CDA data distribution consists of the groups Primary and Secondary data products. However, the user may customize these packages by clicking on them and deselecting certain products, and/or by adding items from the Supporting data products group. Note that the selections are for generic data product types that may or may not exist for all observations. For instance, all but certain calibration observations have a Level 2 event list, but a spectrum is only available for grating observations while images are only produced for imaging observations. Similarly, ACIS products are only available for ACIS observations, HRC products for HRC observations. Selecting products that do not exist for a certain observation does not cause an error to occur; one can, for instance, safely select all primary products for a mix of ACIS and HRC, imaging and grating observations in one selection action and receive only the products that exist for each.

See the Guide to Chandra Archive Data Products for the full list of data products available.

Please be aware that Supporting data products need to be retrieved from a different archive server and that therefore retrievals that include supporting products are inherently slower.

Pressing the View retrieval list button brings up a list of the current contents of the user's shopping cart.

Retrieval List

The user may edit the contents of the shopping cart by selecting items and deleting them.

Browse selected products will bring up a new window with a list of the actual data products that are included in the shopping cart, with file names and file sizes. One should note that the sizes are for the uncompressed products while transfer will take place in compressed form; on average, the compression is about a factor 2. Users are well-advised to check the size of their download before executing the retrieval.

Retrieve selected products will start the retrieval process, either directly to a user-specified directory (Download via application) or to the CDA ftp site (Stage in anonymous ftp area). In both cases the data products are collected in a single tar file. The latter method is significantly faster; in that case a retrieval report will be deposited in the file chaser.log in the user-specified directory which includes the name and location of the tar file. If the size of the file exceeds 2 GB it will be cut into pieces no larger than 2 GB. The files will remain in this location for 24 hours. Use the log file for cutting and pasting the tar file name; on most platforms this does not work well from Java applications directly.

The tar file will contain one directory per ObsId.

If the user is retrieving public data, that is all there is to it. However, if the user requests proprietary data, (s)he will be asked whether (s)he wants to log in to another archive account before the retrieval is executed. The Specify new login and password button may also be used to change the archive account that is in use, for instance, for retrieving another set of proprietary data.

Return to search results allows the user to add more items to the shopping cart or to start a new retrieval process (in the latter case, empty the shopping cart before returning to results).

See the Guide to Chandra Archive Data Products for the list of data products available.

Installation

To download and install ChaSeR, go to the download page. This page offers download packages for various platforms, with and without Java. Installation simply consists of executing the downloaded file. If you are not entirely sure of the Java version that is installed on your machine, we suggest that you take the download version that includes Java and to install it together with and specifically for this application. On Unix-like platforms, the recommended method is to create a symbolic link in one of your bin directories to chaser in the installation directory: do not move the executable .

In addition, system administrators at sites where the run directory is not the same as the install directory need to edit the directory paths lax.dir and lax.root.install.dir in the chaser.lax file to reflect the run directory path. For instance, if the installation is done on the file system /foo in /foo/opt/CDA_SR, but is mounted on user systems as /opt, then the directories will show as /foo/opt/CDA_SR in chaser.lax and should be changed to /opt/CDA_SR.

Note: Window managers like twm and tvtwm not only present a problem for running ChaSeR, but may also affect the installation. See also the FAQ.

In general, if you choose to download ChaSeR without our bundled Java installation, you will need to have Java installed on your machine or accessible from your machine. The Java Virtual Machine (VM) or JRE (Runtime Environment) version that you need is Java 1.3.1. This Java version supports the new Java Swing components. Any version earlier than 1.3 will not work with ChaSeR. The bin directory for your currently installed Java 1.3 also needs to be in your PATH environment variable for InstallAnywhere to automatically find it.

Feedback

Known bugs and current limitations:

1. V&V reports cannot be viewed or retrieved.
2. There are no links to the literature at the ADS.
3. Retrieval of pipeline logs is not supported.
4. It does not work well with older window managers like twm and tvtwm; this is true for all Java applications and cannot be fixed since nobody is maintaining these window managers anymore. See also the FAQ.
5. If the Cancel button is pressed too quickly (a few seconds) after a browse or retrieve is started, the screen will freeze.
6. Selecting a range in galactic coordinates works reasonably well for small rectangles, as long as one stays away from the poles. Large ranges and ranges covering the polses may give surprising results.
7. For certain ObsIds retrieval of secondary and/or supporting products (e.g., aspect solutions) may not return all products that are required.

For feedback and support, go to the CXC Helpdesk.

Please include as complete information as possible.