Access to the HEASARC

on legacy via BROWSE

The data and software archive that is being maintained by the NASA/Goddard Space Flight Center's HEASARC (High Energy Astrophysics Science Archival Research Center) is being moved from its previous location (the NSSDC's NDADSA computer) to the HEASARC's own DEC/System 5000 legacy computer. This switch from a VMS to an Ultrix (DEC Unix) operating system should improve system performance, and has enabled us to redesign our XOBSERVER software to make it mimic a Unix type environment, which is important since the majority of our users are now on Unix systems; it also has enabled to centralize all of our data access methods such as ftp, gopher, WWW/Mosaic, as well as our on-line service BROWSE, on a single computer, legacy. The 'new' archive can be reached by visiting the web site http://heasarc.gsfc.nasa.gov/W3Browse/ (Other ways of accessing the archive are discussed in the companion article by Drake et al. immediately preceeding this article.)

A test version of the XOBSERVER/BROWSE software is already available on legacy , and users can explore the new system: please report any problems that are encountered by leaving a comment when prompted at the end of the session, so that we can eliminate as many bugs as possible prior to the deactivation of the NDADSA XRAY account.

Differences Between the XOBSERVER Commands on NDADSA and legacy

We refer to the command level that you reach once you log in as xray (notice that on legacy the captive account has to be written in lower case), and answer the series of queries with which you are then prompted, as the XOBSERVER environment. Most people who log in to XRAY probably immediately after they get in, type BROWSE DATA_BASE, where DATA_BASE is the name of the database in which they are interested, and enter the BROWSE program, but there are in fact quite a few other possible XOBSERVER commands. In the table below, we list only those commands which are different (in either name or functionality), defunct, and/or new to the version of XOBSERVER on legacy. (For a full list of applications which can be called from the XOBSERVER enviroment on legacy, type 'la'). Notice that in many cases we have retained the VMS name of a command as an alias of the actual Ultrix command.

XOBSERVER Commands

on NDADSA	on legacy
ASC	See Note
BROWSE BULLETIN	bulletin
COPY	cp (or copy)
CREATE/DIR	mkdir
DELETE	rm (or delete)
DIR	ls (or dir)
FITS IMAGE	No legacy equivalent
LOGOUT	exit (or logout)
MKLEPHA	Not implemented on legacy
PURGE	No legacy equivalent
RDPHA	See Note
RDRSP	See Note
RENAME	mv
SEND	put (or send)
SET/DISPLAY	cpd
SET DEF	cd
TYPE	cat (or type)
TYPE /P	more
VIMAT	No legacy equivalent
ZOO/UNZOO	compress/uncompress

Note: Special purpose commands such as these to translate data files in binary formats into ASCII formatted files are not needed on legacy. The XOBSERVER environment contains the FTOOLS applications such as 'fdump', which can read and extract specific data from FITS files.

New XOBSERVER Commands on legacy

email	change user's E-mail address

	The 'email address' command changes the user's E-mail address in the
	registration database.

env 	display current session characteristics

	The 'env' command displays the following session parameters: XOBSERVER
	username, E-mail address, registration date, last login date, home 
	directory path, and graphics plot device if any.  This command is 
	identical to the 'show' command.

get	copy file from user's remote machine
	The 'get file ...' command copies file from user's remote machine.  
	Multiple files must be separated by spaces.  This command is identical
 	to the 'recv' command.

la 	list applications
	The 'la' command prints names of available external applications.

mail	mail a file to your email address
	The 'mail file ...' command sends a file to the user's E-mail address.
	Multiple files must be separated by spaces.

pwd	print current working directory path
	The 'pwd' command displays the current working directory path.

rmdir	delete a directory
	The 'rmdir directory ...' command deletes a subdirectory.  Multiple
	directories must be separated by spaces.

BROWSE on legacy

Once inside BROWSE, the user will not find many apparent differences. Most commands that worked in BROWSE on NDADSA work here also, and in precisely the same way. Only a few things are different, such as a couple of archaic BROWSE commands that are specific to EXOSAT data (i.e., FOTREQ and LIC) that have been discontinued. As of the date of this writing (January 5, 1994), not all data files have been moved to legacy, so some databases (such as the EXOSAT ones) can be browsed on legacy, but do not yet have their data products available: this situation will soon be rectified: in this interim period, in such cases the user should revert to the XRAY account on NDADSA to get the relevant data. By the date on which the captive account on NDADSA is scheduled to be terminated (March 1, 1994), the database on legacy will be fully populated. The data files on legacy, as mentioned above, are actually going be in FITS formats, i.e., be fully transportable between different computers without any need of translation or conversion, as opposed to the files on NDADSA that are mostly in a hodge-podge of obscure, often binary, formats. This, we believe, is a considerable improvement! The new FITS files and their formats will be discussed in the next Legacy issue by Lorella Angelini and Ian George. The important thing as far as the XOBSERVER environment and its various tools are concerned is that this major change in the data files formats will be completely transparent to the user: e.g., the command pp/sp 1 in BROWSE will plot a spectrum of selection 1 just as it always did.

E-Mail Server

HEASARC Database Request E-Mail Server provides a non-interactive user interface to the HEASARC's BROWSE and SQL applications.

The software allows three types of access to the HEASARC DBMS: generic, native, and information. The generic type access provides an intuitive command line interface to perform either cone (coordinate) or name search. The native type access provides the user the flexibility of specifying either BROWSE or SQL native commands. Finally, the information type access provides efficient retrieval of either all archived database or specific database content listing.

The access to the service is via the electronic mail. The server's e-mail address is hdbreq@legacy.gsfc.nasa.gov.

When an empty or otherwise invalid message is sent to the server, the server sends back a reply message composed of the text describing in detail the valid command syntax and some useful examples. Otherwise, the reply message sent back to sender is the actual requested data.

If you have any questions about this service, please contact:

Song Yom
yom@astd3.gsfc.nasa.gov
lheavx::yom
301-286-1364

Summary

There will doubtless be some teething problems with our new XOBSERVER/BROWSE set-up. Please tell us about any problems that you encounter or make suggestions as to enhancements/changes that you would like to see implemented by either leaving a message when you log out of XRAY or by e-mailing the authors directly (drake@lheavx.gsfc.nasa.gov, yom@heagip.gsfc.nasa.gov). We will keep users posted on updates and enhancements to the legacy database through the welcome message that appears after login and in future articles in this journal.

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