Next: 8.5.3 General case
Up: 8.5 Correction for atmospheric TA*
Previous: 8.5.1 Simplest case
Typically, the mean atmosphere temperature is lower than the ambient temperature
near the ground by about 40 K:
; then, the
formula above still holds if we replace Tcal by:
Tcal |
= |
![$\displaystyle ({T_{load}- T_{emi}})e^\tau$](img778.gif) |
(8.33) |
with Temi |
= |
![$\displaystyle T_{sky} \eta_f+ (1-\eta_f) T_{gr}$](img779.gif) |
|
|
= |
![$\displaystyle \frac{(T_{load}+ T_{rec})\times M_{atm}}{M_{load}}-T_{rec}$](img780.gif) |
(8.34) |
![$\displaystyle \T_{sky}$](img781.gif) |
= |
![$\displaystyle (1-e^{-\tau})(T_{gr}-40)$](img782.gif) |
|
Trec, the receiver effective temperature is usually calculated by the Yfactor method using a cold load (usually cooled in liquid nitrogen, i.e. at 77 K)
and an ambient load (e.g. at 290 K).
Y |
= |
![$\displaystyle \frac{M_{hot\_load}}{M_{cold\_load}}$](img783.gif) |
|
Trec |
= |
![$\displaystyle \frac{T_{hot\_load}-Y T_{cold\_load}}{Y-1}$](img784.gif) |
(8.35) |
Next: 8.5.3 General case
Up: 8.5 Correction for atmospheric TA*
Previous: 8.5.1 Simplest case
S.Guilloteau
2000-01-19