updating TEMPO2 clock files

publication date 2022/08/09

TEMPO2 is a pulsar timing package, developed by George Hobbs and Russell Edwards (source code). The purpose of this contribution is to improve the TEMPO2 documentation in some parts that are not fully explained.

HOWTO UPDATE THE CLOCK FILES

Clock files in the GIT of TEMPO2 are not updated very often, so it is necessary to do it manually. The minimum set of files that are necessary to update, are the following:

gps2utc.clk, ut1.dat, utc2tai.clk, eopc04_IAU2000.62-now

1. gps2utc.clk

Requisite:
you can download the TEMPO2 auxiliary programs from archive.org, however these files have some issues for compilation, and here I provide a corrected version of these utilities.
download the BIPM circulars T from this site ftp://ftp2.bipm.org/pub/tai/publication/cirt/
Compile the TEMPO2 auxiliary programs: from the directory where are stored the

cirt.*

files run the following command:

/path/to/update_clkcorr -t gpsutc cirt.*

The updated file

gps2utc.clk

will be named

$TEMPO2/clock/gps2utc.clk.new

Remember that you need all the

cirt.*

files, if some files are missing, you will have incorrect results.
The first files is

cirt.100

, and the the files are update around the 10 of each month. At the next update you need only to download the new files.

2. ut1.dat

Requisite:
download the tempo

do.iers.ut1.new

utility (utility that is part of the program TEMPO)
download the IERS bulletins B from this site http://hpiers.obspm.fr/iers/bul/bulb_new

From the directory where are stored the

bulletinb.*

files run the following command:

/path/to/do.iers.ut1.new bulletinb.* >ut1.dat

Then copy the file ut1.dat to

$TEMPO2/clock/ut1.dat

For more information see this page.
Remember that you need all

the bulletinb.* files

, if some files are missing, you will have incorrect results. The first files is

bulletinb.252

, and the the files are update around the 1st of each month. At the next update you need only to download the new files.

3. utc2tai.clk

Requisite: download the utc2tai correction from this file ftp://maia.usno.navy.mil/ser7/tai-utc.dat
Then manually edit

$TEMPO2/clock/utc2tai.clk

to insert the new leap seconds See also this page.

4. eopc04_IAU2000.62-now

Requisite:
download the Earth orientation parameters series from this file http://hpiers.obspm.fr/iers/eop/eopc04/eopc04_IAU2000.62-now
Copy the file in

$TEMPO2/earth

The file is updated once per month, in the first days each month. At the next update you need to download the new file.

HOWTO ADD A NEW OBSERVATORY

Adding a new observatory is not difficult, but is not well explained in the TEMPO2 documentation. Simply you need to edit the file

$TEMPO/observatory/observatories.dat

, but the TEMPO2 documentation state that:

"For full accuracy, observatory coordinates should be specified in the International Terrestrial Reference System."

Hence the coordinates that are needed in the file

observatories.dat

are XYZ geodesic coordinates in ITRS system. From the above documentation is not clear how to provide the ITRS coordinates, moreover ITRS is a "virtual" system and the realization of this system is the ITRF, as clearly stated by the International Earth Rotation and Reference Systems Service (IERS):

"The International Terrestrial Reference System (ITRS) constitutes a set of prescriptions and conventions together with the modelling required to define origin, scale, orientation and time evolution of a Conventional Terrestrial Reference System (CTRS). The ITRS is an ideal reference system, as defined by the IUGG resolution No. 2 adopted in Vienna, 1991. The system is realised by the International Terrestrial Reference Frame (ITRF) based upon estimated coordinates and velocities of a set of stations observed by VLBI, LLR, GPS, SLR, and DORIS. The ITRS can be connected to the International Celestial Reference System (ICRS) by use of the IERS Earth Orientation Parameters (EOP)."

However the IERS help us with this document, that clarify the following:

"In general the ITRS (and its realizations ITRFyy) are identical to WGS84 at one meter level".

This means that you can insert your XYZ coordinates provided by your GPS (that are based on WGS84 geoid), or in the worst case convert the longitude, latitude, and altitude to XYZ coordinates (a simple C program for the conversion in both direction is available here).

time resolution	error in position
1 as	0.3 nm
1 fs	0.3 um
1 ps	0.3 mm
1 ns	30 cm
1 us	300 m
1 ms	300 km

TEST TEMPO2 PERFORMANCES

It is very important to test if your installation of TEMPO2 is correct, because otherwise you can obtain wrong timing data.

The problem does not comes from the source code, but with the update of the clock files.

A simple way to test TEMPO2 is trying to reproduce the figures in Hobbs, Edwards & Manchester (2006).

Here you can download a shell script that reproduce the figures in the cited article.

Local copy of some important documents

Updating UT1

This is a local copy of the text in this web page:
http://www.jb.man.ac.uk/~pulsar/observing/progs/tempo_ut1.html
I copy the the contents only for preserving it in case of disappearence from the web.


    The final ut1.dat file is held in $TEMPO/clock. Working files and utilities are held in $TEMPO/clock/ut1_updates.
    You should be able to download the latest ut1.dat from http://www.naic.edu/~pulsar// (Arecibo). Save it in the ut1_updates directory and put a copy in the clock directory.
    Otherwise.......
    Feb 08: This method is currently broken, from bulletin 139 onwards (they've changed the format and the script need updating!)
    Browse to http://hpiers.obspm.fr/iers/bul/bulb/  and download the highest numbered (latest) bulletinb.XXX to the ut1_updates directory (and any intermediate bulletins that you may need).
    Run do.iers.ut1 (in $TEMPO/clock/ut1_update) on each bulletin: 

    (Make sure any new leap seconds get added to @leapmjd array in do.iers.ut1). 
    example: do.iers.ut1 bull/bulletinb.128 > ut1.128
    Append ut1.xx to $TEMPO/clock/ut1_updates/ut1.dat. First five numbers should be updates to projected values from previous ut1.xx; last five numbers should be new (projected) values.
    If the last line of ut1.dat is incomplete -- it typically has four entries instead of the usual six -- then the number of entries ('4') should be in column 60 of the last line. Column 60 of other lines should be blank.
    Run check.ut1 to do a 'sanity check' on the new ut1.dat file
    Copy the updated file to $TEMPO/clock/ut1.dat.


Derived from $TEMPO/clock/ut1_updates/0readme.txt by Ingrid Stairs. 23rd Oct 2000 
-  site address updated Oct 2 2002 Caj.

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