The gains of NGST compared to a groundbased 8m telescope
Assumptions (Gillett & Mountain 1998)
SNR = Is . t /N(t): t is restricted to 1,000s for NGST
Assume moderate AO to calculate Is
N(t) = (Is . t + Ibg. t + n . Idc + n . Nr2)1/2
For spectroscopy in J, H & K assume “spectroscopic OH suppression”
When R < 5,000 SNR(R) = SNR(5000).(5000/R)1/2 and 10% of the pixels are lost