Near-Realtime Status Exchange
                   *****************************

                           Werner Gurtner
                       Astronomical Institute
                         University of Bern

                   E-Mail: gurtner@aiub.unibe.ch


The general idea is the following:

- Each laser station generates a one-line status message periodically
  (e.g. every 30 seconds) and sends it to a specific port (7810) on
   a central server (aiuli3.unibe.ch)
  
- The server periodically resends the most recent messages of all sites
  to all open TCP/IP connections on this port.

Example:

Graz          2008-01-24 15:24:10  Lageos2    CUR    11k HTS5241  0.000
Zimmerwald    2008-01-24 15:24:00             DWN
Yarragadee    2008-01-24 15:24:07  Calibrate  CUR   391
Potsdam-3     2008-01-24 15:24:01             OUT
Wettzell      2008-01-24 15:24:05  BeaconC    CUR     0  HTS5231  0.000
Ftlrs_Burnie  2008-01-24 15:24:09             OUT
San_Fernando  2008-01-24 15:24:12  Calibrate  LST   871
MLRO-Matera   2008-01-24 15:23:45  BeaconC    CUR   213  SGF5241  0.000
Herstmonceux  2008-01-24 15:24:15  Lageos2    CUR   642  SGF5241  0.000
-----------------------------------------------------------------------

To just access all available status messages you merely connect to
AIULI3.UNIBE.CH port 7810 with a TELNET command:

   telnet aiuli3.unibe.ch 7810
   telnet aiuli3.unibe.ch /port=7810

or whatever your command for a telnet connection to a specific port is.

There is no user/password needed, you will get the status lines after a few
seconds every 15 seconds. To disconnect you either break with the telnet
escape character or you type "logout".

*******************************************************************************


Near-Realtime Status Exchange
*****************************

1. Status File Generation
-------------------------

Your tracking or data collection program should periodically (e.g., once
every 15 or 30 seconds) generate a one-line message containing the current
status of the site:
                                                   
Example:

Zimmerwald    1998-11-30 09:53:13  Lageos2    CUR   234  CSR005  0.020

Format:

A13           I4   I2 I2 I2 I2 I2  A10        A3  I5   A A7     F6.3    A8
!-----------!.!--------!.!------!..!--------!.!-!.!---!!.!-----!.!----!.!------!

Herstmonceux  2007-05-31 14:38:30  Lageos2    CUR     4  SGF6511  0.000
Yarragadee    2007-05-31 14:38:29  Envisat    LST  1111  HTS6501  0.000
Graz          2007-05-31 14:38:35  Lageos2    CUR    24k HTS6501  0.000


with: - Sitename
      - Date, time (UT)
      - Satellite
        Remove all punctuation marks (hyphens, underscores, blank spaces) and
        capitalise only the first letter of the name (except GPS, GFZ etc).
        Examples: GFO1, Starlette, Lageos1
                  Calibrate: Calibration target
      - Status 
        NXT : Pass to come next, the system is waiting for this pass
        CUR : Currently tracking
        LST : Most recent pass, no new pass initiated
        OUT : Currently not operating
        DWN : Station down (out of order) 
        CAL : Near-realtime calibration
      - Current number of returns.
        Kilohertz-Lasers: If using units of thousands
                          to avoid format overflows, add "k"  
      - CPF set the time bias is referred to
      - Realtime-determined time bias. It should refer to the orbit as
        defined by the CPF set, i.e. the sum of the a priori introduced time
        bias from the time bias file plus the realtime-derived residual
        time bias.
      - Free-format text field

Maximum line length: 80 characters plus linefeed character

Send this line to port 7810 of AIULI3.UNIBE.CH using your own TCP/IP program
or the program EUROSTAT provided in the distribution directory on

  ftp://ftp.unibe.ch/aiub/slr  or  http://www.aiub.unibe.ch/download/slr

You will get in return all the status messages, line by line, from the server,
last line a line of dashes.

Please program your client tolerantly to allow for time-outs
or broken connections.


2. Server Program
-----------------

The server program resides on an Linux workstation in Zimmerwald:

  Internet:  AIULI3.UNIBE.CH
  Port       7810

It collects all available status messages and sends them perodically
to all open connections on port 7810.

These status messages will only contain contributions having arrived within
the last 30 minutes! Messages older than 30 minutes are deleted.

It is not mandatory to send status messages when the site is not operating.
Status message with NXT should not be sent more than a few minutes before
the next pass and LST later than a few minutes after the most recent pass.

3. Other text messages
----------------------

Each laser station may also upload a text message line (< 70 characters)
to the server containing a message to be appended to the station status lines.
The first character of such a line has to be an exclamation mark.

Example:

!This is a test message

The lifetime of each one of these text message is 30 minutes. Later messages
by the same station overwrite the earlier ones. To clear a line send just
an exclamation mark.