The first of the Geo-stationary Operational Environmental Satellites (GOES) -NO/P series, built
by Boeing Satellite Systems was launched on May 24, 2006. The spacecraft, now on-orbit and referred as
GOES-13, carries an Earth Imager, Sounder and a collection of space environment monitors (SEM)
including, for the first time, a solar Extreme Ultraviolet (EUV) telescope. The five-channel EUV telescope
measures the solar EUV energies in five wavelength bands from 5 nm to 135 nm.
We analyze the data from the five EUV channels, collected by the Post Launch Telemetry (PLT)
tests, and compare it to the predictions of precise optical models of the instrument, using two modeling
software- ZEMAXI and FREDII . From our models we detected a misalignment between the SXI and the
XRS/EUV bore-sights that were off by approximately 0.25 degree.
The reference solar irradiation between 1-140 nm in our model was acquired from the TIMED
data taken at the same time as the GOES data. When corrected by the appropriate calibration factors, all 5
channels agreed reasonably well with the TIMED data at zero degree angle of incidence. As expected, the
instruments' responses changed by more than 5% as a function of azimuth angles away from the Sun
center. These changes in irradiation values as a function of angle could be corrected to the values at normal
incidence using photometrical accurate optical models of the EUV instrument.