Download University of LeicesterPLUMERef: PLM-PAY-DetectorProgress

University of Leicester
PLUME
Ref: PLM-PAY-DetectorProgress-019-1
Date: 27/03/2007
Detector progression discussion
L. Evans, P. Molyneux
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27/03/2007
PLM-PAY-DetectorProgress-019-1
first version issued
Notes from meeting with Tim Stevenson
Particle flux
There is not much point in flying a payload that cannot give us meaningful results, so before we
develop the Nanometeoroid detector we need to calculate the number of collisions we can expect
during the satellites lifetime, and decide if this number would be a suitable amount for us to draw
reasonable scientific conclusions from. We need a cumulative frequency plot of something like the
size of particles vs. how often they would be encountered.
Data on expected dust flux can be extrapolated from a model on the Master 2005 CD lent to us by
Tim Stevenson.
Also check James Carpenter’s thesis for LEO plot and calculations.
CCD detector (light flash) vs. metal plate (charge)
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With gas-filled microchannels (metal plate detector), each channel will only fire once. This
may lead to uncertainty in the particle flux we measure.
The charge detector requires a voltage of 1000V. Would we be able to produce this voltage?
We could get a CCD easily by taking the lens off a camera, electronics already there.
It seems like the CCD based detector would be better, but James Carpenter and George Fraser think
it may be unfeasible. However, Tim Stevenson thinks it can be done. We need to look at power, data
storage etc. needed for our detector, and compare to available digital cameras.
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University of Leicester
PLUME
Ref: PLM-PAY-DetectorProgress-019-1
Date: 27/03/2007
Beta meteoroids
Tim suggested we try and study β meteoroids. These are very small particles for which radiation
pressure rather than gravity is the dominant force. Because of this, they travel in a direction away
from the sun. Previously their small mass had made them hard to detect, but we may be able to
detect some if we use a foil of suitable thickness. Whatever thickness we use, if it is thinner than any
currently in use we will need to find what will happen when particles of different mass/energy etc.
impact it. There is a dust accelerator in Heidelberg, and the Open University have one in Milton
Keynes. It is possible that the OU might do the work we need for free.
The detection of β meteoroids would require the detector to be facing the sun at least part of the
time. When the detector is facing the sun, fewer solar panels will be facing it, so we will get less
power. We need to work out if we would still have enough power to keep the satellite operational in
this situation.
We need to estimate the how the flux of β meteoroids (and other particles) is affected by the
attitude of the satellite. How much flux can we expect if the satellite tumbles randomly? What if the
detector always faces the sun? What if it tumbles around the solar vector so it faces the sun some of
the time? Hence we can decide how much attitude control we need.
If the detector faces the sun, we need to consider the CCD baseline. Even though the foil will reflect
most of the visible and IR radiation, some will get through so the baseline will be higher. Will we still
be able to get meaningful results? We need to work out how many photons will be generated by
each light flash (talk to James, also search ‘impact plasma’, ‘photon yield’, ‘impact flash’). For high
energy particles almost 95% of their energy goes to light during impact.
If we decide to use a CCD detector, we need to decide whether to simply use the data from the CCD
as we get it, or have an LED on the other side of the foil and measure the change in the amount of
light going through as more impacts occur.
We also need a system to show us that the detector is working even when there are no dust events.
We could do this by turning on an LED at regular intervals (say once a week) and checking that the
light given off by it is detected properly.
Actions- Aim to complete by the 1st meeting after Easter
Page 2 of 3
University of Leicester
PLUME
Ref: PLM-PAY-DetectorProgress-019-1
Date: 27/03/2007
1. Investigate expected flux of particles using Master CD and James’s thesis.
2. Discuss feasibility of each of the two possible designs with George Fraser, Tim Stevenson and
James Carpenter, decide on one to develop further.
3. Try to work out the power the system will need. For CCD design compare to digital cameras,
for the metal plate design we’d need enough power for 1kV potential difference across it.
4. Research β meteoroids
5. Research expected photon yields when particles hit the foil.
6. Pippa and Laura will write a technical note detailing all the work we’ve done on the system
so far.
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