I need some help interpreting recent GEOS x-ray patterns

[michaelmozina]

http://www.swpc.noaa.gov/ftpdir/plots/x ... 6_xray.gif
http://www.swpc.noaa.gov/ftpmenu/plots/xray.html

For the past few weeks I've been noticing a 24 hour pattern to the GEOS x-ray flux data and I'm wondering if someone could help me out as it relates to the timing of various artifacts in the data. It seems as though there is a 'cut out' that occurs around 4:00 on each day. Is that related to a reboot or repositioning process on GEOS? There also seems to be some repetition on the x-ray spikes from day to day even though the solar cycle has been pretty quiet. Is it possible that some of this repetitive type data could be influenced by the rotation of the Earth rather than a more random solar type process?

 

[MeteorWayne]

Are you talking about the GOES sats used by NOAA? If so, yes at this time of year in late afternoon the satellites can align with the sun, and the signal is lost in the solar flux. By the same token, about 12 hours later (or earlier) the satellite goes into eclipse, so the reduced power cuts out the ability to collect data for a while. You can notice these on the IR satellite cloud images. You see cutouts at those times of the day.

It's particularly noticeable at two times; during the early morning hours you will see dropouts in the IR sat images, which causes gaps in coverage just as (in a more active year) major hurricanes can be approaching the US coast, and in late afternoon, you can see dropouts on TV when the sources are routed through geostationary satellites (loss of signla messages on your cable or satellite or even free TV coverage if they go through Geosationary sats). Of course the exact timing and affects vary by which satllite is in the precise positions at any given time.

Physics

 

[michaelmozina]

Are you talking about the GOES sats used by NOAA? If so, yes at this time of year in late afternoon the satellites can align with the sun, and the signal is lost in the solar flux. By the same token, about 12 hours later (or earlier) the satellite goes into eclipse, so the reduced power cuts out the ability to collect data for a while. You can notice these on the IR satellite cloud images. You see cutouts at those times of the day.

It's particularly noticeable at two times; during the early morning hours you will see dropouts in the IR sat images, which causes gaps in coverage just as (in a more active year) major hurricanes can be approaching the US coast, and in late afternoon, you can see dropouts on TV when the sources are routed through geostationary satellites (loss of signla messages on your cable or satellite or even free TV coverage if they go through Geosationary sats). Of course the exact timing and affects vary by which satllite is in the precise positions at any given time.

Physics

Thanks for the help Wayne. I guess I need to study the orbit of GEOS. I'm so used to SOHO and STEREO now that I don't typically think in terms of regular signal loss, just bakeouts.

 

[MeteorWayne]

It's GOES, not GEOS, BTW

Geostationary Operational Environmental Satellites

 

[MeteorWayne]

KOZ (KEEP OUT ZONE) / ECLIPSE

The GOES satellites encounter two periods, during the year, which the satellites are in the Earth’s shadow. Known as the Eclipse season, these periods require the spacecraft to be totally dependent on onboard batteries for a maximum of 72 minutes daily. Eclipse’s occur from about February 28 - April 11 and August 31 - October 13. The Imager and Sounder instruments are powered down to conserve power, until the daily eclipse is over. There is a significant risk of the sun light directly entering the scanners, as the spacecraft enters and leaves the Earth’s shadow, requiring the Imager and Sounder to be idle prior to and following eclipse. This is known as the “Keep Out Zone”. The seasonal charts describe the GOES-East and GOES-West Imager and Sounder scan frames that are canceled, due to KOZ/ECLIPSE.

http://www.oso.noaa.gov/goes/koz-eclips ... clipse.htm


http://www.oso.noaa.gov/goes/koz-eclips ... all_09.xls

 

[michaelmozina]

Re: I need some help interpreting recent GOES x-ray patterns

KOZ (KEEP OUT ZONE) / ECLIPSE

The GOES satellites encounter two periods, during the year, which the satellites are in the Earth’s shadow. Known as the Eclipse season, these periods require the spacecraft to be totally dependent on onboard batteries for a maximum of 72 minutes daily. Eclipse’s occur from about February 28 - April 11 and August 31 - October 13. The Imager and Sounder instruments are powered down to conserve power, until the daily eclipse is over. There is a significant risk of the sun light directly entering the scanners, as the spacecraft enters and leaves the Earth’s shadow, requiring the Imager and Sounder to be idle prior to and following eclipse. This is known as the “Keep Out Zone”. The seasonal charts describe the GOES-East and GOES-West Imager and Sounder scan frames that are canceled, due to KOZ/ECLIPSE.

http://www.oso.noaa.gov/goes/koz-eclips ... clipse.htm


http://www.oso.noaa.gov/goes/koz-eclips ... all_09.xls

Thank you kindly for the info on "GOES". I appreciate it.

 

[SpaceTas]

That sounds right.
For a similar reason, users of satellite dishes often get poor reception near the equinoxes (Set 21 March 21). The sun is in the same field of view as the TV satellite. The times are not quite at the equinoxes because, of the observers latitude, and geostationary satellites actually do a little figure 8 in the sky. Note you also can glints from the solar panels about this time.
Our group had fun counting the rows of solar cells on satellites using a hish speed photometer on a telescope.