GRBlocator

GRBlocator is a command line utility that determines the position of a celestial object in horizontal coordinates, azimuth and elevation, as well as the minimum height above ground at which it was visible. This is especially usefull to check if a GRB was visible at the sub reflective point of a VLF propagation path, and which layer of the ionosphere were illuminated.

The software needs the observer's position (longitude, latitude, altitude above sea level) and accounts for atmospheric refraction.
Very precise algorithms are used for the computation of the position, but local atmospheric conditions can affect the actual value of the refraction correction.
The atmosphéric refraction must not be taken into accounf for X-rays. The option is disabled by default.

Example

Here are the values calculated for GRB090201:

>GRBlocator.exe --time 20090201174202 --ra "060807" --dec "-46 35 10" --latitude "48 18 29N" --longitude "004 09 46E" --verbose
Observer Location:
	48° 18' 29.00" N  004° 09' 46.00" E  (JN28BH)
	at ground level.

GRB:
	Time:            Sunday, February 1, 2009 17:42:02
	RA (J2000):      06:08:07
	Dec (J2000):     46° 35' 10" S
	RA (precessed):  06:08:22
	Dec (precessed): 46° 35' 17" S


GRB Elevation:             -14.53°
GRB Azimuth:               146.86°
Min GRB Visibility Height: 210.24 km

This calculation is done at the time of the burst (17:42:02 UTC) at the sub reflective point of the path between the DHO38 transmitter and the author's receiving station.
It shows that this GRB was only visible above a height of about 210 km, that is much too high to affect the ionosphere layers involved in VLF propagation.

Download

GRBlocator has been developped in C# under MonoDevelop 1.0. It can also be compiled under Visual Studio 2005.
It has been tested under Linux Ubuntu 8.10/Mono 1.9.1 and under Windows XP/.NET 2.0.

Current version is 1.0.1.0.
GRBlocator binary and source can be downloaded through anonymous SVN at the following address:
https://anonsvn.loudet.org/GRBlocator/tags/

Change Log

• 1.0.1.0 (20090306): addition of option "--refract" to enable/disable the calculation of the atmospheric refraction effect
• 1.0.0.0 (20090301): initial release

Installation

Under Windows, it is necessary to install :

• either .NET 2.0 Redistributable Package, available at: .NET 2.0.
• either Mono 1.9.1 or above, available at: Mono.

Under Linux, it is necessary to install :

• Mono 1.9.1 or above, available at: Mono.

Help

 --ra  --dec 
             --longitude  --latitude  | --locator 
             --altitude  [--refract] [--verbose|--v]

  Options:
    help      Shows this message.
    time      Date and time of the GRB.
              Format is YYYYMMDDHHmmss (e.g. 20060112181215 for 12 January 2006 18:12:15)
              or YYYY/MM/DD HH:mm:ss. Up to 2 decimal seconds are accepted.
    ra        Value between 0 and 235959 expressing the J2000 right ascension of the
              GRB in hours minutes seconds. String representations are accepted.
              Format is HHmmss or HH:mm:ss. Default is 000000.
              Up to 2 decimal seconds are accepted.
    dec       Value between -90 and 90 expressing the J2000 declination of the
              GRB in degrees. String representations are accepted.
              Positive values north of the celestial equator. Default is 0.
    longitude Value between -180 and 180 expressing the longitude of the
              observer in degrees. String representations are accepted.
              Positive values in the eastern hemisphere. Default is 0.
    latitude  Value between -90 and 90 expressing the latitude of the
              observer in degrees. String representations are accepted.
              Positive values in the northern hemisphere. Default is 0.
    locator   Maidenhead locator of the observer. If set, latitude
              and longitude options must not be defined.
    altitude  Real non negative value expressing the height of the observer
              for which the sun altitudes are calculated.
              Expressed in kilometers. Default is 0km (ground level).
    refract   Indicates if the atmospheric refraction is accounted for.
    verbose   Shows legend.
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