GOES Satellite Reports
from the Space Environment Center (SEC)

June 17, 2003 - Problems on the GOES-10 and GOES-12 energetic proton detectors necessitate a change of primary/secondary designations of GOES Space Environment Monitor (SEM) detectors

Background

The GOES 10 energetic proton detectors are showing intermittent, high noise levels in the higher energy proton channels (greater than about 80 MeV). This problem was first noticed in data taken April 26, 2003. (see data plot from this time period and recent data plots). Further analysis revealed that the noise spikes were occurring on the P6 and P7 proton channels and a similar spike was observed at around the same time for several days. These noise spikes occurred late in the UT day and coincided with temperature peaks on the Dome subassembly on the energetic particles sensor (EPS). This pattern is very similar to problems experienced on the P6 and P7 particle channels on the GOES 12 EPS Dome detector prior to their failure earlier this year. The loss of data from the P6 and P7 channels significantly impacts the integral proton flux products above about 10 MeV (e.g., >10 MeV, >50 MeV, and >100 MeV). The P6 channel also impacts our electron measurements; a correction algorithm using proton counts from P6 is applied to the electron count rate to take into account contamination from protons.

GOES Designation Changes effective June 19, 2003

To ensure continued operational monitoring of important energetic particle data, it is necessary to reassign primary/secondary designations for the GOES Space Environment Monitor (SEM) detectors. Beginning 1700 UTC on June 18, GOES 11 (113W) will become the primary satellite for protons. GOES 12 (75W) will continue as the primary satellite for magnetometer, X-ray, and electron measurements. GOES 10 (135W) will be the secondary satellite for all SEM sensors - magnetometer, X-ray, and energetic particles. Because of the degraded state of the proton data on GOES-10, its designation as the secondary source for proton data is a short-term solution. More permanent solutions have been identified and are being evaluated. Users will be notified when we define and schedule a permanent fix.

Sensors	Primary	Secondary
Proton	GOES 11	GOES 10
Magnetometer X-ray Electron	GOES 12	GOES 10
Solar X-ray Imager	GOES 12	no secondary satellite

Users should be aware that GOES 11 is in a storage mode at 113W. Because of the recent problems on the EPS detectors on GOES 10 and 12, we are forced to take the unprecedented action of activating the EPS sensor (for operational purposes) on a storage satellite - GOES 11. The GOES-11 EPS Dome detector does not appear to be experiencing the problems encountered with both the GOES 10 and 12 domes. However, the satellite is spinning in storage mode, with a nine- minute spin period; consequently, there will likely be short outages when the transmit antenna is hidden by the spacecraft body. These outages have diurnal and seasonal variations that are difficult to assess, but data loss is expected to be minimal. This spin mode will likely produce small variations in the measured fluxes due to the changing look direction of the sensors.

The electron processing algorithm has been modified in response to the high noise level that recently developed in the GOES 12, P6 proton channel. A correction algorithm is applied to the electron count rate to take into account contamination from protons. The standard correction algorithm uses proton counts from the P3, P4, P5, and P6 channels. The modified correction algorithm no longer uses data from the P6 channel. As a result, the proton correction algorithm gives a smaller correction at all times. The electron fluxes will not be as low during time periods of flux minima, and the correction will not be as extreme during large proton events. For a greater than 2 MeV electron flux of 100 particles/(cm²-s-sr), this modification will result in a flux reduction of roughly 10%. For an electron flux of 1000 particles/(cm²-s-sr), the modification will be roughly a 1% flux reduction.

Operations on the Solar X-Ray Imager (SXI) on GOES-12 will not be impacted by these changes. There is no secondary SXI.

General GOES Information

The electron measurements will differ somewhat between GOES 10 and GOES 12. This difference is due to the different geomagnetic latitudes of the two spacecraft. Both GOES 10 and GOES 12 are located on the geographic equator, but due to the tilt of Earth's dipole magnetic field, GOES 10 (at 135 degrees west longitude) is at a lower geomagnetic latitude than GOES 12 (at 75 degrees west longitude). Because of the different geomagnetic latitudes, GOES 10 on average measures a larger electron flux than GOES 12. The relative variations in flux from time to time are roughly similar at the two spacecraft locations.

GOES 8, 10, and 12 data are archived at the National Geophysical Data Center for Solar - Terrestrial Physics

Questions and comments are welcome. SEC.Webmaster@noaa.gov

GOES Online Data Files

GOES 11 differential proton channels and integrated flux data lists will be restarted June 18. Other data lists will continue as before. Proton data lists users should note that GOES 11 is now primary, and GOES 10 secondary.

Legend, Text, and Header Changes

Beginning June 18, the following data plots show GOES 12 primary, and GOES 10 secondary, except the Integral Proton Flux plot.

The following SEC products, GOES 12 is primary and GOES 10 is secondary for data, legends, text, and headers. Reports that show older data, now show all GOES 12 data (except Proton data is from GOES 11). No user changes are needed.

April 8 2003 Announcement
GOES 8 data stops, GOES 12 data begins

On April 8, SEC began using data from the GOES 12 satellite, and stop using GOES 8 data. SEC tracks two GOES satellites and designates one as the primary GOES satellite and the other the secondary GOES satellite. With the end of GOES 8, the primary/secondary designations changed to GOES 10/12. However, on May 15, 2003 these designations were changed again to GOES 12/10, see description at top of this page.

GOES 12 has the new Solar X-Ray Imager (SXI), which acquires real-time, operational images of the solar x-ray flux. GOES 12 is the primary satellite for the SXI. There is no secondary SXI.

Many SEC online products contain GOES data or information based on GOES measurements. The May 15 changes are shown in the tables above.