Subject: Administrative: ATMS Calibration Algorithm Changes made to
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Topic: ATMS Calibration Algorithm Changes made to IDPS Block 2.0

Date/Time Issued: February 14, 2017  1745 UTC

Product(s) or Data Impacted: S-NPP ATMS TDR/SDR and NDE ATMS BUFR,
MiRS,
NUCAPS

Date/Time of Initial Impact: IDPS Block 2.0 Transition To Operations
TBD

Date/Time of Expected End: IDPS Block 2.0 Transition To Operations TBD

Length of Outage: N/A

Details/Specifics of Change:
Changes made to the ATMS Calibration Algorithm IDPS Block 2.0 will
reduce
brightness temperature bias for the ATMS TDR/SDR.  The downstream
NDE MiRS
and NUCAPS products will also be affected by this change. This
change is
expected to occur when Block 2.0 transitions to operations (no
earlier than
March 1, 2017).

Algorithm Change Details:
1) In Block 1.2, the non-linearity factor was implemented by the early
NPOESS contract with a sign error. In Block 2.0, the sign was
reversed in
the calibration equation.

2) In Block 2.0, the non-linearity term in calibration equation
is derived
through a quadratic fitting of all the prelaunch TVAC data. In this
fitting, the bias in the cold target calibration is significantly
reduced.
It is believed that the cold end bias may result from the antenna
emission.


3) In Block 1.2 ATMS data, the calibration equation was written in
terms of
brightness temperature. Since brightness temperature is approximated
from
the Planck function using a Rayleigh-Jeans (RJ) approximation,
corrections
must be made as a LUT to brightness temperature due to the RJ
approximation, especially for ATMS high frequencies (W/G bands). We
believe
use of RF approximation is unnecessary and is inconsistent with the
approach for NOAA legacy instruments (AMSU/MHS).  In Block 2.0, the
calibration equation is derived in terms of radiance. The calibrated
earth
scene radiance is converted to antenna brightness temperatures
(TDR) using
the full Planck function.

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<div dir=3D"ltr"><div class=3D"gmail_signature"><div
dir=3D"ltr"><div><div =
dir=3D"ltr"><div><div dir=3D"ltr"><div><div dir=3D"ltr"><div><div
dir=3D"lt=
r"><div><div dir=3D"ltr"><div><div dir=3D"ltr"><div><div
dir=3D"ltr"><div d=
ir=3D"ltr"><div dir=3D"ltr"><div>Topic: ATMS Calibration Algorithm
Changes =
made to IDPS Block 2.0</div><div><br></div><div>Date/Time Issued:
February =
14, 2017 =C2=A01745 UTC=C2=A0</div><div><br></div><div>Product(s)
or Data I=
mpacted: S-NPP ATMS TDR/SDR and NDE ATMS BUFR, MiRS,
NUCAPS</div><div><br><=
/div><div>Date/Time of Initial Impact: IDPS Block 2.0 Transition
To Operati=
ons TBD=C2=A0</div><div><br></div><div>Date/Time of Expected End:
IDPS Bloc=
k 2.0 Transition To Operations TBD</div><div><br></div><div>Length
of Outag=
e: N/A</div><div><br></div><div>Details/Specifics of
Change:=C2=A0</div><di=
v>Changes made to the ATMS Calibration Algorithm IDPS Block 2.0
will reduce=
 brightness temperature bias for the ATMS TDR/SDR.=C2=A0 The
 downstream NDE=
 MiRS and NUCAPS products will also be affected by this change. This
 change=
 is expected to occur when Block 2.0 transitions to operations (no
 earlier =
than March 1, 2017).</div><div><br></div><div>Algorithm Change
Details:</di=
v><div>1) In Block 1.2, the non-linearity factor was implemented by
the ear=
ly NPOESS contract with a sign error. In Block 2.0, the sign was
reversed i=
n the calibration equation.</div><div><br></div><div>2) In Block 2.0,
the n=
on-linearity term in calibration equation is derived through a
quadratic fi=
tting of all the prelaunch TVAC data. In this fitting, the bias in
the cold=
 target calibration is significantly reduced. It is believed that
 the cold =
end bias may result from the antenna
emission. =C2=A0</div><div><br></div><=
div>3) In Block 1.2 ATMS data, the calibration equation was written
in term=
s of brightness temperature. Since brightness temperature is
approximated f=
rom the Planck function using a Rayleigh-Jeans (RJ) approximation,
correcti=
ons must be made as a LUT to brightness temperature due to the RJ
approxima=
tion, especially for ATMS high frequencies (W/G bands). We believe
use of R=
F approximation is unnecessary and is inconsistent with the approach
for NO=
AA legacy instruments (AMSU/MHS).=C2=A0 In Block 2.0, the calibration
equat=
ion is derived in terms of radiance. The calibrated earth scene
radiance is=
 converted to antenna brightness temperatures (TDR) using the full
 Planck f=
unction.</div><div><br></div><div>This message was sent by <a
href=3D"mailt=
o:ESPC.Notification@noaa.gov">ESPC.Notification@noaa.gov</a>. You
have been=
 sent this and other notifications because you have opted in to
 receive it.=
 If for any reason, you wish to unsubscribe, please contact ESPC Help
 Desk =
at <a
href=3D"mailto:ESPCOperations@noaa.gov">ESPCOperations@noaa.gov</a> o=
r (301) 817-3880. Please note: it make take up to two business days
to proc=
ess your unsubscribe
request.</div><div><br></div><div><br></div></div></di=
v></div></div></div></div></div></div></div></div></div></div></div></div><=
/div></div></div></div>
</div>

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