Subject: GMS-5 Data
From: root@asarginv.org.ar
Date: Wed, 17 May 95 13:10:30 3

Gms 5 has only 1 new  infrared micron band added. (6.5 to 7.0) (water vapour)
The infrared thermal channel has been split in two (10.5 to 11.5, 11.5 to 12.5)

MDUS SETUP

Frequency 1687.1 Mhz
Modulation BPSK, NRZ-M
SPEED      660 KPS

SDUS SETUP

FREQUENCY 1691.0 MHZ
MODULATION:  AM
BANDWDITH   260 KHZ
OUTPUT SIGNAL 2.4 KHZ

GMS S-VISSR DATA
FREQUENCY    1687.1
MODULATION   DIFFERENTIALLY ENCIDED BPSK, NRZ-M
BIT RATE     660 KBPS FIXED RATE
E.I.R.P.     56+/- 1.5 DBM ( AT ANTENNA ELEVATION ANGLE OF 20 DEGREES
BANDWDITH    LESS THEN 2 MHZ
DATA VOLUME  329 872 BITS/LINE INCLUDING SYNC SCRAMBLING
DATA CODING  BYTE COMPLEMENTING AND PN SCRAMBLING
DATA SEQUENCE MOST SIGNIFICANT BIT (MSB) FIRST

Nominal longitude is 140 degrees East (at zero degrees lat., of course).

The S-VISSR is at 1687.1 MHz (same as GOES Mode A/AAA). It is a BPSK/NRZ-M
digital bit stream at 660 Kbps.

The LR-FAX (WEFAX) is at 1691.0 MHz. It is a relatively standard WEFAX signal
(AM modulation of a 2.4 KHz subcarrier, which FM modulates the RF). It has one
unusal characteristic - the RF bandwidth is 260 KHz ! Also, JMA had plans to
add a second subcarrier with a 4800 bps digital data stream (conventional
weather telex data), but I am not sure of the status of this link.

I am out of date on the product scheduling. It was Full disk 8 times a day
(every three hours), two successive full disks (for wind calculation) 4 times
per day, and hourly northern hemisphere half disks. The standard observations
started at 33 minutes after the hour.

S-VISSR transmission is done similar to GOES, ie. a few scan lines lag between
the observation and transmission to the main processing site and retransmission
to the users.

There used to be no transmission overlap between S-VISSR & LR-FAX. This may
change with the addition of two more IR channels on GMS-5.

GMS-5 is a replacement for GMS-4, there should be no break in service. S-VISSR
users can continue to operate with no changes for the two new IR channels if
they wish. GMS-5 has been launched and is undergoing checkout. I am not sure of
the exact date of switchover of operations from GMS-4 to GMS-5. As far as I
know only one of GMS-4 or GMS-5 will be operational at a time. GMS-4 will be
kept as a backup for GMS-5 as long as possible.