ANTICIPATED TRACE DARK CURRENT (originally mailed on 25 May 1997) (slightly revised on 23 July 1997 to go into the newly forming WEB "reports") This is incomplete but it records some aspects on this topic. It is based on the small amount of data we obtained during instrument-level TB/TV and we'll get more data during the observatory level testing. Please remember that both the offset/pedestal and the actual dark current change with temperature. 1) Susan predicts the early part of the mission will have the CCD varying from like -53 to -62 C around the orbit. 2) Although for some of the data during TB I get ridiculously low dark current rates I think the system had a rate of like 0.3 electrons/ sec at -65 C. This, by the way, is what we said prior to launch for MDI and then shortly after launch it was measured at like 0.7. Dexter, is the level of inversion the same for TRACE as for MDI? 3) The rate changes about a factor of 4 for 10 degrees. This is a lot more than the factor of 2 in 8 degrees that seems to be a rule of thumb so I looked at some old Janesick curves and the factor of two for 8 degrees seems to be at room temperature and the factor of 4 for 10 degrees seems just fine for temperatures like -65 C. Bob Stern later confirmed this "finding" as well know reality. 4) Susan's predicts then translate into something like 0.5 to 2.0 e/sec around the orbit which is 0.03 - 0.15 DN around the orbit for the A amp (X3 less for B) 5) If we go a factor of two higher for the "MDI Orbital effect" and a factor of 4 higher for 10 degrees of thermal margin the number become more like 0.2 DN to 1.2 DN around the orbit 6) Those are still pretty small; like less than read noise. However we do have an operational heater on the CCD with the same sort of control system as the other operational heaters so one could set a deadband and duty cycle and smooth this out. AND LET'S RUN WITH THE OPERATIONAL HEATER DOING ITS THING DURING SOME OF THE UPCOMING TB/TV TEST TO SEE HOW IT WORKS AND WHETHER IT INTRODUCES NOISE.