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GK-2A Test Week

July 20, 2019 - sam210723

Between Monday 2nd and Friday 5th of July 2019 the KMA NMSC conducted testing of their new geostationary weather satellite GEO-KOMPSAT-2A (GK-2A). This post is a summary of the testing carried out during this period, as well as some observations regarding new data types and formats.

RF Carriers

Around 9:50 AM KST the COMS-1 L-Band transponder was switched off to make way for the GK-2A LRIT and HRIT carriers. Initially only a strong CDAS carrier containing raw sensor data from GK-2A was visible.


LRIT and HRIT carriers containing processed GK-2A data appeared later in the day. HRIT was running at the usual 3 Mbps (3 MSps QPSK), but the data rate of LRIT had increased to 256 kbps (512 kSps BPSK). This faster data rate is what COMS-1 LRIT used before it was reduced to 64 kbps (128 kSps BPSK) in late March.

GK-2A LRIT and HRIT carriers were present for the rest of the week until around 11:00 AM on Friday 5th when the L-Band transponder was switched off. A few minutes later the COMS-1 L-Band transponder was re-enabled, followed by LRIT and HRIT carriers.


Observations

Only minor protocol changes were seen during the testing period. Most notably, all sensor wavelengths were combined into a single virtual channel (VCID 0) rather than each wavelength having its own VCID.
VCID COMS-1 GK-2A Testing
0 Visible Full Disk (all channels)
1 Short-wave Infrared not used
2 Water Vapour not used
3 Infrared 1 not used
4 Infrared 2 Additional Data
5 Alpha-numeric Text Alpha-numeric Text
63 Fill / Idle Fill / Idle

The observation interval of Full Disk images was drastically reduced from 3 hours to 10 minutes, allowing smooth animations to be created. No other image types such as COMS-1 Enhanced Northern Hemisphere were seen during the testing period. Full disk false colour animation (03/07/19)
All GK-2A test data was encrypted in the same way COMS-1 is, except using a different key. Thankfully this key was from the same key table used by COMS-1. See "COMS-1 LRIT Key Decryption" for a detailed look at the key table file and decryption process.


Normal COMS-1 operation has been restored and will continue to operate until GK-2A is officially brought online later this year.