Information
for Visitors about Computers at GMRT
General Information
There are 2 computers viz. gtac1
and gtac2 placed in terminal room for
astronomical data analysis specifically reserved for GTAC observers.
In addition, there are four computers viz. astro1, astro 2,
astro3 and astro5 are
kept in Terminal room at GMRT central building. A
computer
astro4 is kept in sub-wing near control room. These machines are
similar to gtac1 and gtac2 and can be used for astronomical data
analysis.
Disk spaces of several GB will be routinely available in /DATA/
partition
of each of the above machine. If there is not enough space, please
contact the system administrator. Please note that within a day of
your departure from the GMRT, all the files created by you will be
deleted without backup. It is the responsibility of the GTAC user to
take proper backup of their data, before they leave GMRT. It
is expected that the users will bring their own media for back-up.
However, in emergency, efforts will be made to get a limited quantity
of DDS-3 tapes for Rs. 450/-.
In the computer room, a network printer is available called
'npgcc'. From a
Linux machine, command to print is: lpr -Pnpgcc [files] or 'lpr
[files].
LAPTOP Users at GMRT:
There are tables kept in the sub-wing near the control room (passage
from control room to server room). You can plugin
your laptop and do the following settings:
Name: guest.gmrt.ncra.tifr.res.in
IP Address : 158.144.18.25
Netmask : 255.255.255.192
Default GateWay : 158.144.18.20
DNS Server : 158.144.18.17
Preparing
for observations:
Source Parameters:
Create source list in your home area in similar to the source list
in /btemp2/source/vlacal.list. The spacings between
the columns are important. The sample command file is in
/btemp2/cmd/sample.cmd. Once you are ready with the
source list and command file, inform operators. They will check these
and upload them to online machine.
Frequency Settings:
A standard form available in the control room where the frequency
settings can be filled in.
Every GTAC user should fill in this form indicating the observing
frequency, bandwidth, integration time and other
details. Giving verbal instructions can lead to wrong settings due to
language problems.
Computers astro1, astro2, astro3
and astro5 has a DDS3 DAT tape
drive with device /dev/nst0. On a DDS3 tape, 10 to 11 GB of GMRT data
(GMRT raw data and/or FITS) can be put by tar command or through
aips. Default data area where the GMRT raw data is recorded is
/rawdata for USB data
and /rawdata1 for LSB data. In this area data will be present in the
subdirectory called by day and month e.g. /rawdata/17may;
/rawdata1/17may.
During the Observations..
Some offline analysis software are available to look at the data.
For any path confusion, source /etc/bashrc for
bash and /etc/csh.cshrc or /etc/cshrc for csh. Source /astro/RC for
bash shell or source '/astro/RC.csh' for
csh/tcsh
shell. Run the software and say explain. This will give help for the
software's usage.
The following programmes will be useful for any GTAC user.
1. ltahdr : Gives info about the GMRT raw data, which is in 'lta'
format. The rawdata for USB comes with an extension .lta and
LSB with .ltb. Usage: ltahdr -i . Check
'ltahdr --help' for details.
2. tax: Graphical interface to plot the data. Using this programme, one
can monitor the phase and amplitude stability of the data while the
observation is in progress. Type 'tax' and then type 'explain' for more
details.
Converting GMRT raw data to
FITS format:
The GMRT data can be converted into FITS file using two programmes,
listcan and gvfits.
1. listscan : List the scan in the ltafile for converting to FITS
format. Go to /DATA/; make sure there is enough
space. Run listscan (eg: listscan ).
This will create a file with .log extension. Open this file with your
favorite editor. The parameters you might need to change are the
output FITS file name, CLASSIC_NORM (normalisation by self), removing
unwanted antennas or scans, giving path to the FLAG file etc.
1. gvfits : Convert GMRT (lta) data to FITS format. Run gvfits on the
above log file (eg: gvfits test.log). This will take some time
depending on the size of the input file.
Miscellaneous offline programmes:
The following programmes might not come in use for GTAC users
if there are no problems in the observations.
1. xtract: Extract data from lta file in various formats.
2. ltacomb: combines lta files.
3. ltaclean: cleans up ltafiles with gliches in it. First one or two
records can also be removed using this programme (similar to 'QUACK' in AIPS).
4. ltasel: allows data averaging selection.
5. relta: allows averaging in time.
6. offstop: Stop fringe offline by providing suitable tables antenna
coordinates and fixed delays.
7. tcalibbp : Program for bandpass calibration.
How to get into AIPS:
To use aips on these machines, after login do following:
gtac1% newgrp aips
gtac1% source
/usr/aips/LOGIN.CSH (for csh) or source
/usr/aips/LOGIN.SH (for bash)
gtac1% aips
Prefer to use aips id 1010, 1020, 1030, 1040 and 1050 for
visitor1, visitor2, visitor3, visitor4 and visitor5 accounts
respectively. There is /DATA partition kept for aips data purpose.
Make required number of sub directories here and edit .dadevs
appropriately.
Backup of the
data:
It is the
responsibility of the visitor to take backup of their data. No backup
is taken for the /DATA and /analysis area and user
has to take his own backup before he leaves GMRT site. All the files
from the visitor account will be deleted the day following the day
visitor leaves GMRT.