# Presentation: 950931

## Leonid Meteor Shower 2003Proposed Polar Operations Plan

- The Polar teams have requested to follow the operations plan used in 2000 & 2002
- The Polar despun platform will be fixed such that the instruments will be pointed away from the radiant of the Leonid Meteor shower for a 48-hour period centered on the predicted maximum peak of the fluence (within sun tolerance ranges)

## Leonid Meteor Shower 2003Proposed Polar Operations Plan

- MFE, EFI & PWI have no high voltage supplies so no special procedures are necessary
- UVI will not ramp down the high voltage supply but will take the precaution of closing the window
- Hydra will ramp down their high voltage
- The remaining teams have requested not to ramp down their high voltage supplies
- The EFI, Hydra, MFE, PWI & UVI teams have all approved the request that the other instruments do not cycle their high voltage supplies

## Leonid Meteor Shower 2003Proposed Polar Operations Plan

***VIS***: Based on the model fluence predictions for the Leonid meteor shower, the maximum probability of the VIS camera being struck is about 1 in a million.
- In comparison, the number of hours of sporadic meteors that would be equivalent to the total predicted fluence from the 2003 Leonid meteor shower is 2250. Therefore, in 3.1 months of normal operation, the risk of spacecraft damage from sporadic meteors is equal to the entire risk from the 2003 Leonid meteor shower.
- Pointing of the platform instruments away from the radiant of the Leonid meteor shower will insure that in the highly unlikely event that a meteoroid strikes the spacecraft, none of the debris will enter the VIS aperture

## Leonid Meteor Shower 2003Proposed Polar Operations Plan

***CAMMICE***:  The MICS instrument failed in 2002, so there are no operational issues.
- Unlike MICS, the CAMMICE/HIT instrument does not have high voltage. It is a solid state detector telescope. Therefore, there are no high voltage issues at all with HIT.
- There is nothing operationally that can be done to make it safer.

## Leonid Meteor Shower 2003Proposed Polar Operations Plan

***CEPPAD***: The instrument contains no high voltages exposed to the space environment. Even if a puff of plasma were generated by a hit somewhere on Polar, the plasma could not get to the high voltage which is internal.
- There is the remote chance that cycling the power could lead to a change in the performance of the power supply or even failure.
***CEPPAD/SEPS***: The high voltage is only 30V which typically falls below the region where one expects problems with HV arcing. The risk of ESD is considered to be minimal since the density of the dust environment is no worse than the charge particle environment in which the instrument operates daily.

## Leonid Meteor Shower 2003Proposed Polar Operations Plan

***TIDE***: The instrument has curved plate analyzers with good HV design, that do not allow line-of-sight trajectories to reach the detectors, and therefore, are not susceptible to Leonid damage.
- Small meteoric particles have no direct path to the detectors and entrance to the detector is limited by collimators on each head. Fragments from a collision with the electrostatic** **mirrors also have no direct path to the detectors, so that damage to the detectors from impact is highly unlikely. Damage to the electrostatic mirrors due to impact would occur whether the high voltage is on or not. The increase in plasma from nearby impacts outside the instrument presents no problem since the instrument is protected from over counting.

## Leonid Meteor Shower 2003Proposed Polar Operations Plan

***TIMAS***: If a meteoroid strikes Polar it will produce a small puff of cold plasma well away from exposed portions of the TIMAS instrument. The TIMAS input ion optics will pass only the ionized portion of the cold plasma above 15 eV. TIMAS is designed to accept extremely high fluxes of ions.
- In order for TIMAS to be fatally injured by a Leonid Meteorite, two conditions are necessary: A) The puff of plasma must occur near the electrostatic ion deflection plates located inside the exposed input baffles.  B) The electronics designed to be able to handle a high voltage discharge fail.
- The meteorite would have to pass through the vulnerable area of the baffle which is about 10cm2. The maximum flux of expected Leonids is 0.001 km-2s-1. So the probability of a hit in the vulnerable area in 3 hours is about 1 in 100 million.

## Leonid Meteor Shower 2003Proposed Polar Operations Plan

***PIXIE***: The instrument is well shielded and grounded so ESD is not a problem.
- PIXIE is a radiation-measuring device and it could not work in its intended environment if the ESD protection was not intrinsic to the design.
- The greatest potential problem is arcing in the high voltage power supplies. Past calculations have showed that the dust environment was more benign than the radiation environment resulting from a flare