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Failures encoutered during build and test of Swea sensor instrument

MAVEN-Swea sensor pre-shipping review - December 1-2/2011

2MAVEN-Swea sensor pre-shipping review - December 1-2/2011

Maven/ SWEA is a remake of Stereo/ SWEA for which 4 models were developped (2 X FM + 2 x EM)

The proposal to CNES for Maven/ SWEA was to build an instrument for MAVEN as close as possible to Stereo one (limited funding and manpower)

A limited number of changes were identified by IRAP and SSL (Stereo to Maven doc) due to:o Different mission profileo Stereo anomalies considering dataso Improve the instrument

These changes induced some anomalies, failures or new concerns

Some failures or anomalies were already present on Stereo

3MAVEN-Swea sensor pre-shipping review - December 1-2/2011

When commanding HV deflectors to zero, the deflectors HV was not zero.

The same supply return line was used to command HV deflectors and to supply MCPs high voltage, So when commanding the deflectors to zero there were not zero on deflector HV command but differents positive values depending of differents MCPs high voltage supply currents.

(Deflectors HV offsets did not comply to ICD)

4MAVEN-Swea sensor pre-shipping review - December 1-2/2011

Proposition: • Connect all interface connector spare wires to analog ground both on sensor side and on

electronic box side (SSL) to reduce the changing impedance of analog return line and so reduce deflectors HV command offsets.

• IRAP to make a calibration of deflectors HV offset vs MCP HV value.

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Radiation doses expected more important than for Stereo

Make a new thicker electronics boards housing part (2.5mm). (mech. Part #23)

MAVEN-Swea sensor pre-shipping review - December 1-2/2011

6MAVEN-Swea sensor pre-shipping review - December 1-2/2011

Three M2x4 CHC obturator fixation screws suspected to be in detector field of view.

Solution: replaced by 3 M2x4 FHC screws as on drawing here.Obturator modified to fit FHC screws.

7MAVEN-Swea sensor pre-shipping review - December 1-2/2011

On Maven project, after SSL simulations, it was decided to raise top deflector by 1mm and drop bottom deflector by 0.3mm to have better deflexion homogeneity.After this operation, it appeared that part #32 was partly in detector field of view.

Solution: Slightly modify part #32(see mechanical parts list & drawing)

8MAVEN-Swea sensor pre-shipping review - December 1-2/2011

Following part stress analysis: Osram SFH421 LED not qualified

Tests according to “EEE-INST-002 Instructions for EEE parts selection, screening, qualification and derating.” were made by Hirex with SSL agreement.

LAT tests on samples Life test (1000 hours) Radiation tests up to 20KRad at low dose flow (smaller or equal to 360 rad (SI)

per hour)

Tests results successfuls

(See Hirex reports)

9MAVEN-Swea sensor pre-shipping review - December 1-2/2011

Following part stress analyser: Vishay HV resistor had under rated voltage

Vishay HTS68 (1GΩ) rated 2KV Vishay HTS523 (1GΩ) rated 5KV

10MAVEN-Swea sensor pre-shipping review - December 1-2/2011

Following part stress analyser: diodes JANTXV1N6642 has peak inverse voltage overstress (100V)

Were replaced by JANTXV1N6638 (rated 150V)

11MAVEN-Swea sensor pre-shipping review - December 1-2/2011

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