Seshen25 station report for Tog meeting at ASTRON
            (March 2006)


1. Observations

Seshan station participated in VLBI activities in 2005 October and
2006 February sessions.

2. Antenna 

The antenna drive and control system has been upgrade from July to
August in 2005. The new control system was used in 2005 October and
following sessions.  The performance are summarized as : Azimuth
slewing rate : 1 degree/second (60 degree/minute) Azimuth slewing
range: -78 degree to 430 degree Elevation slewing rate : 0.6
degree/second (36 degree/minute) Elevation slewing range: 5 degree to
88.5 degree These parameters have been updated in new released sched
version.  The tracking is more stable and slewing is more
flexible. Problems due to antenna has reduced herefrom.

The main reflector was re-adjusted using the holography surveys from
5th to 18th November 2005. The surface accuracy (rms) was improved up
to 0.55 mm from 1.20 mm.

3. Recording system and Field System

There are only eight BBCs (BBC01 to BBC08) and one IF distributor
available at the Shanghai VLBI Station since September 2005. (The
other six BBCs and one IF Distributor have been used for tesing a
new-built 50m telescope in Beijing )

A new power supply of Mark 5A (for two disk banks with 250G) was
installed and will be used soon.
	
We kept updating the FS software system with the latest version. The
current version 9.7.7 in use works well at the Shanghai VLBI
Station. The Mark 5A recording system also works well in past EVN
sessions. We have bought another SWT FS computer for software
debugging and backup.

A formatter problem was taken place during the session EL033B (Feb
17). The formatter time frequently reset to 2000. We are sorry that
the problem resulted in failture of the whole session. The problem was
fixed on Feb 19th. (Thanks for helpful advices and suggestions from
VLBI colleagues)

4. H-maser

The H-maser (MHM2010) works well since May 2004. In July 2005, we
tested the atomic clock. Results show that it works in good
conditions, and its performance is consistent with technical
specifications.

5. receiver system

An L-band cryogenic, dual-polarization receiver was installed in
September 2005.  It starts working since November 2005 in EVN
sessions.  It was identified with swapped polarization in Network
Monitoring experiment N05L5. (Thanks for JIVE support scientists.)

It was found that upper half of channels (ch9--16) were not found
fringes in session F05C1. The signals from ch9--16 are not sent to MK
IV formatter because the link between them was not connected. The
problem was fixed right away after F05C1. The vacuum pump of C band
receiver stopped working occurationly during the October 2005
sessions, as a result, the system noise temperature is a big higher.

K-band system was not so good in 2005 October sessions. The reason was
not certain yet. Apparently the noise temperature was much higher. No
fringes were found in N05K2.

A new S/X feed was installed in December 2005.

6. Future plan

6.1 Developing Mini DBBC for Lunar project.
This work is being carried out.

6.2 a new S/X band receiver was built, and will be applied soon.