IRAC Instrument Handbook - IRSA - California Institute of Technology

IRAC Instrument Handbook
into a red limit, then IRAC would send the C&DH (via the special engineering data on the low-speed
line) a request to be turned off. If a telemetry point other than one affecting a single focal plane goes into
a red limit, IRAC would also send the C&DH a request to be turned off.
2.5 Sensitivity and Saturation
2.5.1 Sensitivity
To estimate the sensitivity of IRAC in flight, where possible we use the measured properties of Spitzer
and IRAC from IOC/SV; otherwise we use the required performance based on the design specifications.
The sensitivity to point sources (in flux density units) is based on the following formula:
where the scale factor is
the background current is
and the effective exposure time is
N pix
2 2
σ = BTex
+ ( BTex
f F ) + R + DT
(2.1)
ex
ST f
ex
p
QηTη
I A∆λ
S = (2.2)
hλ
B = SI f Ω f
(2.3)
ex
bg
F
S
pix
Instrument Description 16 Sensitivity and Saturation
ex
T = T − 0.
2N
(2.4)
F