[noaaport] GRB specific information.

If you don't operate or care about GRB ground station operations, please just hit delete.  For those that operate a GRB ground station, here is some important information from Toby Hutchings with NESDIS on the upcoming roll-out of GOES 19 into operations:

Greetings User Community,

Broadcasting answers to frequently asked questions to the community.  Below you will find the latest topic of discussion.

Is there an expectation that some GRB users may need to re-point their antennas in connection with the G16 "nudge", and then re-point again for the transition to G19 GRB? If so they might like to know the specific date of the nudge.

"Short answer:  Assuming GRB users are operating an antenna 7m or smaller, they should not have to re-point their antennas during the G16 to G19 transition.

Longer answer:  GOES 16 is being nudged from 75.2 deg W to 75.5 deg W.

Using our HR5 antenna here at WCDAS as a reference, the difference in ground antenna pointing angles between these two orbit locations is as follows:

HR5 - GOES 16 (75.2 deg) = 179.50 deg AZ and 44.95 deg EL

HR5 - GOES 16 (75.5 deg) = 180.06 deg AZ and 44.85 deg EL

The difference in ground antenna pointing angles is 0.47 deg AZ and 0.1 deg EL

Assuming a GRB user is operating a 7 meter antenna, the half-beam width calculations of that antenna at 1.686 GHz is as follows:

0.25 deg = 0.25 dB

0.35 deg = 0.5 dB

0.5 deg = 1 dB

0.86 deg = 3 dB

Since the expected pointing angle offsets are 0.47 deg AZ and 0.1 deg EL, the expected downlink degradation should be between 0.5 and 1 dB.  This expected degradation should not cause an issue with users assuming that their antennas are peaked on G16 at its current location.  If they are not peaked currently, this move and resulting degradation could cause issues.

Additionally, any users with antennas larger than 7m will have narrower beam widths and thus experience a greater signal drop from this move.  For example, if our 16.4m HR antennas were not autotracking, we would experience a 6dB drop in signal from this move if we did not re-peak."

Special thanks to Matt Sullivan from our WCDAS Team for providing a detailed response!

-

Stonie Cooper, PhD

Software Engineer III

NSF Unidata

address@hidden

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