I concur with the previous statements about this likely being thermal.  At least that's what we decided last time we discovered this feature.  
Does anybody have an easy way to plot temperature(s) over the course of the entire mission?  That'd be a nice confirmation.

Tony


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Anthony Case

Astrophysicist

High Energy Astrophysics Division (HEAD/SSXG)

Center for Astrophysics | Harvard & Smithsonian

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On Mon, May 17, 2021 at 1:43 PM Jody Wilson <jkwilson@guero.sr.unh.edu> wrote:
There was also a 6-month periodicity in the old proton swoosh summation, and there's a 6-month periodicity in the SEPI components (individual detectors, Andrew is investigating this further) that is indistinguishable from a longitudinal variation.  Mark's explanation may be the reason for all of these - I just wanted to point out that 6-month periodicities have shown up before.

-Jody


On 5/17/2021 1:28 PM, de Wet, Wouter wrote:

Mark,

 

Ahh, yes that makes sense! When I cut everything below the peak the 6-month periodicity in the low LET flux data all but disappears.

 

Thanks for the quick response. It looks like I will need to cut everything below roughly 0.3 keV/micron out of the analysis.

 

Wouter

 

From: Mark D Looper <mark.d.looper@aero.org>
Date: Monday, May 17, 2021 at 1:11 PM
To: "de Wet, Wouter" <wouter.dewet@unh.edu>, "crater-team@lists.sr.unh.edu" <crater-team@lists.sr.unh.edu>
Subject: Re: Interesting Artifacts in CRaTER Data: 6-Month Periodicity in Low LET Fluxes (including a strange anti correlation)

 

Caution - External Email

If I remember correctly, that’s due to thermal noise in the lowest PHA channels, which is periodic because of the differing sun exposure as the orbit changes.  I will see if I can find some plots that I made near the beginning of the mission which showed this.  It is why I discard the lowest PHA channels and never look much below the proton peak – the data are not valid down there.

 

--Mark

 

Mark D. Looper
Space Sciences Department
The Aerospace Corporation
M/S M2-260
P.O. Box 92957
Los Angeles, CA 90009-2957
Mobile: 310-529-3406
Voicemail: 310-336-6302

Publications: https://www.loopers.org/curvitae.html

 

From: Crater-team <crater-team-bounces@lists.sr.unh.edu>
Date: Monday, May 17, 2021 at 7:07 AM
To: crater-team@lists.sr.unh.edu <crater-team@lists.sr.unh.edu>
Subject: [Crater-team] Interesting Artifacts in CRaTER Data: 6-Month Periodicity in Low LET Fluxes (including a strange anti correlation)

All,

 

While working on the final processing of the observed CRaTER Flux vs. LET data, I have found an interesting artifact.

 

I have been looking at the Flux vs. LET vs Time data for the entire mission so far.

 

  • For the smallest LET values, there seems to be a 6-month periodicity in the observed flux, see the ‘wavy’ red edge in Figure 1 below.
  • When I divide everything by the flux observed in August 2009, I get the flux ratio shown in Figures 2 and 3 below. When looking at the flux ratio, the 6 month periodicity becomes very clear.
  • One interesting thing I also notice is that it seems like there is an anti-correlation between the flux in lowest LET bins (< 0.25 keV/micron) and the slightly higher LET bins  (> 0.25 keV/micron).

 

Has anyone else observed this yet? Any thoughts about what is causing this?

 

Thanks,

Wouter

 

 

Figure 1: Flux vs. LET vs. Time

 

 

Figure 2: Flux Ratio vs. LET vs. Time (3-Dimensioal)

 

 

 

Figure 3: Flux Ratio vs. LET vs. Time (2-Dimensioal)


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