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Subsections


Applications

COCO Conversion of Celestial Coordinates

The COCO program can be used to convert between various coordinate systems (for example, celestial to galactic) or different equinoxes and epochs. COCO is a STARLINK program written by Pat Wallace. Its commands are as follows:


   I p       specify input coordinate system (p defined below)
   O p       specify output coordinate system (       "       )
   F x       specify RA mode:  x = H or D (hours,degrees)
   R y       select report resolution:  y = H, M or L (high,medium,low)
   S         display current settings
   <coords>  perform conversion  (or = to repeat last coordinates)
   ?         show format of <coords>
   /<file>   switch to secondary input file <file>
   H         list the commands
   E         exit
Parameters p for I and O commands:


   4 [eq] [ep]   equatorial, FK4
   B [eq] [ep]   like FK4 but without E-terms
   5 [eq] [ep]   equatorial, FK5
   A  ep         equatorial, geocentric apparent
   E  ep         ecliptic
   G [ep]        galactic

   eq            equinox, such as 1950 (optional B or J prefix)
   ep            epoch, such as 1984.53 or 1983 2 26.4
Input format:


       RA     Dec       PM       Px    RV
      h m s  d ' "  [s/y  "/y    ["  [km/s]]]
   or
      h m s  d '
   or
      h m    d '
   or
      h      d

    (proper motions default to zero in FK5)
Notes:


Example:


<- 12 -62       ! convert from b1950 to j2000 (the default mode)

 = 12 00 00.000 -62 00 00.00  B1950.00  B1950.00  FK4  0.000    0.0
-> 12 02 34.461 -62 16 42.53  J2000.00  J2000.00  FK5

<- 12 23 -62 23 ! convert from b1950 to j2000 (the default mode)

 = 12 23 00.000 -62 23 00.00  B1950.00  B1950.00  FK4  0.000    0.0
-> 12 25 47.406 -62 39 36.88  J2000.00  J2000.00  FK5

<- o g          ! convert from b1950 celestial to galactic

   Conversion is to:
      Galactic, epoch B1950.00

<- 12 23 -62 00

 = 12 23 00.000 -62 00 00.00  B1950.00  B1950.00  FK4  0.000    0.0
-> 299.95345    0.44640  B1950.00  galactic (II)

<-

NH - HI Galactic Column Density

The NH program, written by P. Giommi provides, for a specified right ascension and declination. He gives a value for galactic HI hydrogen column density. The NH program uses the data contained in the ``Bell Laboratories H I Survey" (A.A. Stark, et al., 1990, privately distributed tape) and interpolates for a given sky position. To run the NH program from within the XRAY account, simply type:


HEASARC>  nh
Give an RA and Dec as prompted and the program will return a value for galactic NH. Note that the Bell Lab 21-cm survey data only cover regions of the sky north of declination -40 degrees.

PIMMS and Viewing

PIMMS (Portable, Interactive, Multi-Mission Simulator) is a simulation program initially tuned for ASCA but written in a general enough way as to be useful for other missions. PIMMS can perform flux conversion to and from count rate or count rate to count rate conversion, given a spectral model. The current version of PIMMS can also simulate simple ASCA SIS images. The name PIMMS reflects three crucial design goals.

Complex spectral simulation has not been included within PIMMS. That would require a rather extensive effort, not only initially but also to keep up with the ever increasing set of theoretical models. PIMMS is currently limited to three analytical models (blackbody, power law, and Bremsstrahlung) and a limited grid of Raymond-Smith models, each with a simple cold absorber. More complex spectral model can be imported to PIMMS by way of an ASCII file that can be generated using XSPEC or by users' own programs. When planning a time-critical observation, it may be necessary to know when a satellite can observe a particular target. Viewing is a stand-alone utility program which calculates sun angle constraint and outputs the visibility window (i.e., times of year when the satellite can point at the target). Viewing does not have information on up-to-date orbital elements of satellites; thus it is impossible to predict a detailed viewing pattern (Earth occultations, SAA passages etc.) or the efficiency of observation with this program. Some satellites may have additional constraints (e.g., thermal) that Viewing does not take into account. However, in the case of ASCA, for instance, there are currently no factors which can make the observation of a target on a given date impossible, as long as the Sun angle constraint is satisfied. For other missions, consult respective mission description documents.

Using PIMMS and Viewing

PIMMS and Viewing are available as part of the HEASARC Online Service and may be used from the xray account. PIMMS and Viewing can also be obtained by anonymous ftp from ``heasarc.gsfc.nasa.gov" under the directory asca/nra_info/pimms. This directory includes a README file and several compressed tar files. Help files and an up-to-date user's guide, as well as the source code and data files, are also provided by anonymous ftp.


next up previous contents
Next: Miscellaneous Up: HEASARC Users Guide Previous: SQL Interface
Michael Arida
1998-04-10