EPHIN Radiation Analyses, Results, and Radiation Belt Studies|
Welcome to the ACIS EPHIN analyses and results home page. ACIS, the
Advanced CCD Imaging Spectrometer, is an instrument built by a
team from the Massachusetts Institute of
Technology's Center for Space
Research and the Pennsylvania State
University for the Chandra
Unexpectedly, various analyses by various people from a number of
institutions have shown that ACIS exhibits an on-orbit charge-transfer-inefficiency
(CTI) problem. For a more detailed treatment of how this problem
surfaced, the various ground analyses performed, as well as important
background information, please read the
report produced for the ACIS
front-side anomaly workshop at Penn State University.
The purpose of this page, however, and the analyses presented below,
is simply my attempt to try and accumulate all of the EPHIN analyses in one place
so that it's sum may shed light on the ACIS FI CTI problem. To that end, what I
have done so far is to simply post work that I have done as well as a
brief summary of my analyses. Usually, I provide an "EMAIL" link that
you can follow to read an email in which I more thoroughly describe
the plots, my analysis and its relevance. This page is by no means complete yet nor
is the work just of mine alone. I have added work that others have
done and will continue to add the work of others as well.
As one would expect, this page is always under constant construction with
new items being added regularly. If you would like to suggest
something that you believe ought to be accessible from this page, let
6 November 1999
NOTE: Links are
generally to either postscript files or GIF/JPG images. If your
netscape browser doesn't automatically bring these documents in their
respective viewers, press the SHIFT key and LEFT CLICK your mouse
button simultaneously to download the files to your computer.
EPHIN PLOTS AND RADIATION BELT ANALYSES
In this section, you will be able to find links to plots I have
produced as well as a brief summary of my analysis.
UPDATED TABLE 1
- EPHIN Radiation
History (GZIP'ED)                           EPHIN
The above link is a postscript file that contains all of the EPHIN
data to date on a log-linear plot. The file is gzipped and is LARGE
(currently 33 megs zipped). Superimposed on the EPHIN data, are
various time spans: SIM translation, radmon disable/enable, and the E1
time spans (from bottom to top; note that SIM translation only started
on Day 260). Time spans are clearly labelled.
CXO's Radiation History
For January, 2000
CXO's Radiation History
For February, 2000
- MSFC Magnetopause Model VS EPHIN
(Nov, Dec, & Jan 99) (GZIP'ED)
Bill Blackwell and Joseph Minow (Sverdup/MSFC) have been working on a probablistic
magnetopause model. Their modelling approach is to examine the
probability that Chandra is located in one of the following
phenomenological regions: solar wind, magnetosheath, or
magnetosphere. That is, they determine the probability that Chandra
encounters one of those regions at any point along its orbit. I have
taken their 25%, 50%, 75%, and 95% magnetosphere probablity time spans
and have overlaid it on the EPHIN data. The labels identify each time span.
Chandra encountering the magnetosphere region is a necessary but not a
sufficient condition for safing the instruments during radiation belt
- Chandra Radiation Belt Events As
A Function of Time and Altitude
Just as the title implies, the above link takes you to an ASCII table
that provides time-tags and the corresponding altitudes for the
various radiation belt events. In particular, the times and altitudes
when the SIM was translated to and from HRC-S, RADMON DS/EN times and
altitudes, as well as the Electron 1 times and altitudes are provided.
- Chandra's Altitude
Straightforward plot of Chandra's altitude as a function of
time. Similar to the EPHIN radiation history plots, superimposed are
various time spans: radmon disable/enable (bottom bar), SIM
translation, and E1, E2, P1, and P2 time spans, in that order.
- SCE150 vs. Altitude                                                            EMAIL
- SCP4GM vs. Altitude
The above two links are plots of EPHIN's lowest energy electron (0.25
< E < 0.70 MeV) and proton (5.0 MeV < E < 8.3 MeV) channels as a
function of altitude. The vertical line in all plots signifies the
60,000 km crossing. These plots demonstrate that EPHIN sees
significant electron and proton fluxes out to 12-13 R_e.
- EPHIN Flux Plots: Day 280 to Day 290                         EMAIL
- SCP4GM As Function of Time and Altitude: Day
283 to Day 288
- SCP4GM versus Altitude: Day 281 -
From Day 260 onwards, ACIS has seen no further significant CTI
change. However, recent analysis suggests there was a slight CTI
increase sometime between Days 280 and 290. The first link provides
plots of all EPHIN electron and proton channels during this time
frame. The second link is a plot of the lowest energy EPHIN proton
channel as a function of both time and altitude. The third plot is
just a simple 2D plot of P4 flux vs. altitude during 4 radiation belt
passages during this time frame. Please click on the "EMAIL" link to
read more about this analysis.
- SCP4 Flux On Day 286 and In The P4
Flare               EMAIL               NEW P4 THRESHOLD?
This plot pulls just the EPHIN P4 data from perigee passage on Day 286
(top panel) whereas the bottom panel is a plot of just the P4 flare
prior to perigee passage. From this plot, I determined a fluence of
5x10^5 EXTERNAL P4 proton counts/cm**2/sr.
- Chandra' Altitude versus Time on Day 286                 EMAIL
Simple two panel plot of CXO's altitude as function of time on Day
286. The bottom panel in the above postscript file is CXO's altitude
between Day 286.4 and Day 286.5.
EPHIN AND ACE CME PLOTS, ANALYSES AND CORRELATION STUDIES
- ACE CME Electron Plot                                                    EMAIL               ACE PROTON ALERT LEVELS
- ACE CME Proton Plot
- EPHIN CME Plots
- EPHIN CME Plots -- Magnified
Given an email from Mark Bautz suggesting threshold values to use with
ACE satellite data so that ACIS would not be damaged in a changing
radiation environment, I produced the above plots for a CME that
occurred on October 14, 1999 (Day 287). The first two links are to ACE
electron and proton plots. The horizontal line in the electron plot is
the ACE electron threshold that Mark specified. The last two links are
plots made from EPHIN data.
- ACE Electron and Proton Data From The Past Year                              EMAIL
- ACE Proton Plots Spanning A Year Over
Various Hour Intervals
ROB CAMERON: The first plot shows one-hour averaged electron and proton fluxes over
the past year. The red datasets cover the recommended energy ranges.
Mark Bautz' suggested electron flux limit (100 e/cm^2-s-sr-MeV) and
proton flux limit (10^5 p/cm^2-s-sr-MeV) (each for one hour) are shown
on the plots, together with Steve O'Dell's proton flux warning level of
3.10^4 p/cm^2-s-sr-MeV. The second plot shows proton fluence measures over the past year.
Fluence has been calculated over timescales ranging from 1 hour to 256
hours (= 10.67 days).
Please follow the "EMAIL" link for a deeper and more greater
discussion and analysis.
RADIATION BELT MODELS: DISCUSSION
Bill Blackwell and Joe Minnow's attempt to produce a probabilistic
radiation environment model based on randomly sampling solar wind
data. There is a link near the top of this page that compares this model
against the EPHIN data.
Web Page Designed and
Shanil Virani - firstname.lastname@example.org
(Please feel free
to send me any comments or suggestions!)
First Attempt: 1 October 1999 ----- -->
--Latest Attempt: 17 July 2000