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ASCA Guest Observer Facility

The ASCA Archive


Introduction

Between 1993 Apr 5 and 2000 July 15, ASCA performed 3079 separate observation sequences. These are now all publicly available at the HEASARC, and can be accessed using the "ascamaster" catalog in Browse.

The ASCA archive opened on 15 November, 1994, and is accessed via the online service of the High Energy Astrophysics Science Archive Research Center (HEASARC). This page describes the archive contents and how to retrieve the data. A brief overview of how to retrieve ASCA data, the processing and data products produced is available in the "Getting Started Guide", while a full description of ASCA data analysis is available in "The ASCA Data Reduction Guide" which is also available in via anonymous FTP at: legacy.gsfc.nasa.gov/asca/doc/.

All data have been processed using revision 2 data processing. We currently plan to re-process all ASCA data within the next year or so. The main purpose of this will be to incorporate the final calibration of time-dependent gains of both the GIS and the SIS; we do not anticipate major changes in the directory structure or in the type of data products.

All ASCA data can be searched and retrieved using the ascamaster table under Browse. Instead of going via Browse, the entire archive can be directly accessed via the legacy.gsfc.nasa.gov anonymous FTP under the directory legacy.gsfc.nasa.gov/asca/data/rev2. Though the user should be warned that this is a full listing and can take some time. Further details about retrieving the data are given below.

An ASCA publication and bibliography listing can be retrieved.


Archive File Structure

ASCA data is most conveniently stored (and labeled) by the 8-digit SEQUENCE-NUMBER which is assigned to each pointed observation and generally consists of about a day's worth of consecutive data. The data for a particular observation sequence is quite large (up to 200 Mbytes or more) and thus the data is divided into eight more manageable sub-directories (TELEM, AUX, CALIB, SCREENED, UNSCREENED, IMAGES, LCURVES, and SPECTRA). For a typical analysis not all files are necessary.

Full details can be found in the Getting Started Guide.


ASCA Science Data Processing

All the ASCA archival data have been processed into a user-friendly form at the ASCA Data Facility, part of the NASA Goddard Space Flight Center's Astrophysics Data Facility. All ASCA data have been processed with the script called Revision 2 (REV2). Details of REV2 processing (including the standard data selection criteria) can be found in the Getting Started Guide.


Accessing the ASCA data.

Public ASCA data may be retrieved in any one of the following ways:
  • By anonymous FTP at legacy.gsfc.nasa.gov under the rev2/[sequence number] directories.

  • By the World Wide Web at HEASARC Browse. Select the mission ASCA and then the database "ascamaster." Data products can be located and extracted via this interface .

In all cases the same basic file structure is used to store the data.

Intrepid explorers of the ASCA public archive should note that the PV data, especially those taken in the first few months, are not always optimized for scientific investigation of the targeted object. Many observation were made for instrument calibration and contain frequent mode changes and non-standard parameter setting for which instrument responses are not available. The observation modes and instrument setting during the latter PV and AO phase are more stable. If in doubt, please ask the ASCA GOF: visit the Feedback form.

Anonymous FTP

Data can retrieve by anonymous FTP in the usual way (% = UNIX prompt}:

 %ftp legacy.gsfc.nasa.gov 
   (username: anonymous, password: your_e-mail_address)
 %cd asca/data/rev2/seq_num/sub_dir
 %binary
 %[prompt]
 %[m]get file_name[s]
 %quit

To find match the sequence number to an observation, use BROWSE (see below) or the file in asca/docs/ascapublic.txt.

Example 1: Getting the cleaned products. 

mget asca/data/rev2/60000000/images/*.gif    <-- get all the gif images
mget asca/data/rev2/60000000/screened/*.evt    <-- get the merged cleaned
                                                  event list data
mget asca/data/rev2/60000000/images/*.img    <-- get all the sky FITS images

Example 2: Getting all the screened event files

mget asca/data/rev2/60000000/screened/*       <-- get all the screened
                                                  event files plus the
                                                  observation catalogs.

Example 3: Getting all the unscreened event files

mget asca/data/rev2/60000000/unscreened/*     <-- get all the unscreened
                                                  event files, and the
                                                  observation catalogs 
mget asca/data/rev2/60000000/aux/*.mkf.gz      <-- get the mkf files

World Wide Web

To access the Browse interface go to: HEASARC Browse. Choose the ASCA mission, and begin the search with the name or coordinates of the object, or the parameters of the observation. The hyperlinks then lead to the data. The gifs can be displayed, to give a quick look at the data.


Contacts

If you have any questions, comments, suggestions or problems using the ASCA archive please visit the Feedback form.


Acknowledgements

The creation of the ASCA archive has been a joint effort by the ASCA GOF in the Laboratory for High Energy Astrophysics, and the ASCA Processing Team in the Astrophysics Data Facility (ADF).


If you have any questions concerning ASCA, visit our Feedback form.

This file was last modified on Thursday, 14-Jun-2007 08:34:14 EDT

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