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One of the things we've talked about adding to the digi report is a pedestal summary. But we could also add something that would
supplement the calf_mu_trend test in the CAL CPT. Are you still in charge of digi reports?
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I'll dig up the email I sent to Eric Charles with the daily monitoring plots we used for OSSE, and I'll forward that to you.
Eric
Here's a reminder of the contents of the CGRO/OSSE Daily Standard Plots
See "page 4" of the Daily Standard Plots here.
See "page 5" of the Daily Standard Plots here.
From: grove@ssd5.nrl.navy.mil
Subject: Some GRO daily monitoring plots
Date: 3 November 2006 7:15:22 PM EST
To: echarles@slac.stanford.edu, borgland@slac.stanford.edu
Cc: eduardo@slac.stanford.edu
Eric,
Here's a teaser of the OSSE on-orbit daily standard plots, sent to you without enough explanation. We made a series of plots in the production data processing for every single day of the 9-year mission as part of the data integrity and instrument health monitoring process. Both plots are for day 91/271, i.e. the 271st day of 1991, the entire day. On "page 4" you're seeing count rates in energy bands from detector 4 of 4. On "page 5" you're seeing count rates in ancillary particle detectors. At the top of both pages is a context timeline, with geomagnetic rigidity, marks for SAA times, GRB messages from BATSE (the equivalent of GBM, from the same guys at Marshall), marks for the "primary" and "secondary" sources in each orbit (OSSE viewed two targets per orbit, nominally on complementary sides of the Earth).
Look at page 5.
The SAA appears on page 5 in the CPMPR and CPMEL (Charge Particle Monitor Proton and Electron detector) time series. See that 6 of the 16 orbits each day have a significant SAA passage, with 2 relatively modest SAA passes. Note that they are marked also by the bold bars in the Rigidity time series. BTW, the CPM was a small plastic scintillator (3/4" diameter, 3/4" long) turned on at all times.
Note from the CPD$R* plots (the Charge Particle Detectors 1 through 4) that the orbital particle rate modulation is bigger on non-SAA orbits than on SAA orbits, i.e. the particles that aren't trapped in the belts (i.e. aren't in the SAA) are more strongly modulated on those orbits that don't pass through the SAA. This is an interesting consequence of a 28 deg orbit from an Eastward launch. BTW, the CPD was a plastic scintillator paddle, about 24" in diameter, over the aperture of each OSSE spectroscopy detector (4 spec detectors, so 4 plastic CPDs) used in the trigger logic as an active veto.
Look at page 4.
Here you see the same Rigidity panel, plus a bunch of other rates associated with OSSE spectroscopy detector #4.
The first panel below the rigidity is SHIELD$R4. These are total veto count rates in the four, thick CsI shield segments that surrounded the main spectroscopy detector. The threshold was about 10 or 20 keV, as I recall.
The DTL$R4 panel shows the deadtime in the low-energy channel. I've forgotten the units, I'm embarrased to say.
Next is the neutral particle rate (mostly utter nonsense). The OSSE detectors were NaI-CsI phoswich detectors, with the CsI(Na) acting as an active shield to the rear of the NaI(Tl), which was used as the spectroscopy detector. The detectors were fairly massive: 13" diameter, 4" thick NaI and 3" thick CsI (or maybe I have the Na and Cs thicknesses backwards, it's been a while). From the pulse shape, one can deduce the depth of interaction (or at least deduce whether the scintillation came from NaI, CsI, or a mix). Neutrons have a different pulse shape than gammas, electrons, or protons, and this channel was meant as a neutron monitor. It's heavily polluted with overspill from real gammas, so really all you were looking for here was a big, huge spike above the wandering trend. Ignore it.
The bottom 5 panels are counts per 16 sec (I believe those are the right units) in each of 5 energy bands. For example, the bottom panel ".05 C/4" is the rate of 50-100 keV photons in detector 4, counts per 16 sec. Note the large exponential decays in the bottom three bands, i.e. up to the 300 keV to 3 MeV band. This is the decay of iodine-128 activated in the SAA from the 127I in NaI and CsI. It's a beta+ emitter with a 1.5 or 2 MeV endpoint and a 30ish minute lifetime. Note that we're saved a little from this activation in GLAST by having the CAL zero suppression at 2 MeV, and by the fact that each CsI xtal is a lot smaller than the OSSE phoswich.
In the 3-10 MeV and >10 MeV bands, note the orbital modulation again. Obviously it's not the gammas that are modulated here, but the particles. You're looking here at prompt decays from passing GCRs and residual light.
Unlike in the GLAST band, in the nuclear gamma regime (say 50 keV to 10 MeV), observations are overwhelmingly dominated by local background. The instrument is a lot hotter than the sky. So to observe an astrophysical source, we pointed the collimated detectors at a source for 2 minutes, then scanned off source by a couple collimator attenuation lengths (say 5 deg), then chopped back to source, then off, etc etc etc for 9 long years. There were only a handful of sources that were visible in these 16-sec samples (Crab nebula, ~6 BH binary transients, and one or two neutron star transients, as I recall). So when we saw the 2-minute chopping in these standard plots, we knew we would detect an extremely bright source in the detailed spectroscopy analysis. The other dozens of OSSE sources were visible only in incoherent sums of source-minus-background over one or two weeks of observing.
Eric