SWEA Plume Impingements

1. Mars Atmosphere and Volatile EvolutioN (MAVEN) Mission SWEA Plume Impingements

2. Thruster Operations Impacting SWEA • Payloads concerned with thruster operations • SWEA (high voltage) Requires Flux < 1E-11g/cc • If thruster plumes impinge on science instruments apertures above acceptable levels options are: • 1) Turn off science during planned thruster operations • Extended durations may impact science data collection requirements • 2) Rework/Optimize configuration • Initial configuration is based on heritage MRO control system - Science instruments placed to optimize FOV while staying away from current thruster plumes (geometrically) • Planned thruster operations • MOI (200N) and TCS (22N) thruster maneuvers • Prior to Science Phase (instruments will be off and not deployed) – 5 to 8 maneuvers • During Science Phase – 15 to 40 maneuvers • RCS (1N) thruster maneuvers every 24 hours ranging from 2.5-13 minutes

3. Plume Analysis at SWEA Plume Density on Spacecraft (kg/m3) from all 1 N and 22 N thrusters -Density is higher on SWEA than on any other part of the spacecraft -Max plume density at the SWEA detector is 1E-06 kg/m3 (Limit is 1E-8 kg/m3) Plume density at APP instruments, SEP, and SWIA is well below the limit of 1E-8 kg/m3. Heat flux is also very low. NOTE: 200N MOI thrusters not included in analysis because SWEA will be stowed and off during MOI Heat flux from all thrusters (W/m2) The max heat flux is 6E3 W/m2 or 4.4 Suns at SWEA 1 N thrusters do not impinge on SWEA

4. Rotating SWEA boom Rotated SWEA boom about pivot point, keeping SWEA instrument aligned with Z axis Goal was to reduce plume heat flux below 1 Earth Sun (S0=1367 W/m2) by rotating the instrument away from the thrusters 35 degree rotation needed 0 deg = 4.4 S0 30 deg = 1.46 S0 35 deg = 1.0 S0 40 deg = 0.62 S0 45 deg = 0.38 S0

5. SWEA rotated by 35 degrees Plume density (kg/m3) from all thrusters with SWEA rotated by 35 degrees -Max on SWEA detector is 1.7 E-7 kg/m3 -Exceeds limit of 1E-8 kg/m3 We will not be operating SWEA during 22 N thruster operations Heat flux (W/m2) from all thrusters with SWEA rotated by 35 degrees -Max on SWEA detector is 1340 W/m2

6. Updated SWEA Stowed Configuration01/11/10 SWEA CANTED 45O

7. SWEA DEPLOYED 135O SWEA SWEA BOOM SWEA SUPPORT FITTING SWEA Deployed01/11/10

8. SWEA FOV Delta Original SWEA Location SWEA Rotated 35O SWEA FOV SWEA FOV SWEA FOV SWEA FOV

9. SWEA FOV 01/11/10

10. SWIA FOV 01/11/10 SWEA remains inside of the SWIA FOV

11. Star Tracker FOVs 01/11/10 New SWEA position does not impact the Star Tracker FOVs

12. Thruster Impact Summary Plume analysis for 22N and 1N thrusters Drove out a needed change to SWEA configuration Prior to configuration change With all 22 N thrusters firing at once: Max plume density at the SWEA detector is 1E-06 kg/m3(Limit is 1E-8 kg/m3) The max heat flux is 6E3 W/m2 or 4.4 Suns After 35 degree rotation of SWEA (away from spacecraft) With all 22 N thrusters firing at once: Max plume density at the SWEA detector is reduced to 1.7e-7 kg/m3 (Limit is 1E-8 kg/m3) Forces SWEA HV to be powered off during all 22N thruster operations The max heat flux is 1340 W/m2 approximately 1 Sun No constraints on instrument operations during 1N thruster operations (desats) Assessment of SWEA 35 degree rotation Allows Spacecraft to meet its 1% plume impingement requirement Best compromise between thruster heating and spacecraft blockage of SWEA FOV. reduces thruster heating levels at SWEA down to ~1 Sun (at 1AU), May require a change to the surface properties of the SWEA deflectors (which get exposed to this heating) The SWEA FOV blockage by the spacecraft at 45 degrees to the Sun is acceptable (and meets the Level 1 requirements). Configuration changes are readily adapted into SC configuration SWIA and Star Tracker FOVs not impacted