Particles and Fields Package MAVEN System Requirements Assessment August 11, 2009 David Curtis

1. Mars Atmosphere and Volatile EvolutioN (MAVEN) Mission Particles and Fields Package MAVEN System Requirements Assessment August 11, 2009 David Curtis Particles and Fields Package Manager

2. The PFP Ensemble LPW- EUV SWIA LPW SWEA MAG SEP (sunward FOV not shown) MAG STATIC Solar Wind Ion Analyzer (SWIA) - SSL Solar Wind Electron Analyzer (SWEA) – CESR / SSL Langmuir Probe and Waves (LPW) – LASP / SSL Plus Extreme Ultra-Violet (LPW-EUV) - LASP Solar Energetic Particle Detector (SEP) - SSL Magnetometer (MAG) – GSFC Supra-Thermal and Thermal Ion Composition (STATIC) - SSL

3. PFP Block Diagram 10cm

4. Requirements Flowdown • PF Requirements derive from the following Level 2 Requirements • Mission Requirements Document (MRD) • Environmental Requirements Documents (ERD) • Mission Assurance Requirements Document (MAR) • PF Level 3 requirements flow down from these to the PF Requirements Document • PF to Spacecraft accommodation requirements flowed through the ICD (Level 3) • PF System requirements flowed back up to the MRD/ERD • Magnetics, Electrostatics, etc. • Verification methods are assigned to requirements • All these requirements documents are captured and linked up in the Project DOORS database

5. STATIC Measurement Requirements • STATIC measures Low- and medium-energy ion composition, energy, and direction: • Densities, velocities, and temperatures of suprathermal H+, O+, O2+, and CO2+ above the exobase with the ability to spatially resolve magnetic cusps • Derived Level 3 measurement requirements:

6. SWEA Measurement Requirements • SWEA measures properties of solar wind electrons that can drive escape: • Energy distributions of solar wind, magnetosheath, and ionospheric electrons to determine the electron impact ionization rate, with an energy resolution sufficient to distinguish ionospheric photoelectrons from solar wind electrons • Electron angular distributions to determine magnetic topology, with the ability to spatially resolve magnetic cusps. • Derived Level 3 measurement requirements:

7. SWIA Measurement Requirements • SWIA Measures properties of solar wind ions that can drive escape: • Density and velocity distributions of solar wind and magnetosheath ions to determine the charge exchange rate and the bulk plasma flow from solar wind speeds down to stagnating magnetosheath speeds • Derived Level 3 measurement requirements:

8. SEP Measurement Requirements • SEP Measures solar energetic particle input into upper atmosphere: • Solar energetic particles that can interact with the upper atmosphere, with a time resolution sufficient to capture SEP events. • Derived Level 3 measurement requirements:

9. MAG Measurement Requirements • MAG measures solar-wind interactions and “mini-magnetospheres” • Vector magnetic field in the unperturbed solar wind, magnetosheath, and crustal magnetospheres, with the ability to spatially resolve crustal magnetic cusps. • Derived Level 3 measurement requirements:

10. LPW Measurement Requirements • LPW shall measure electron temperature and number density measured in situ: • Thermal electron density and temperature from the ionospheric main peak to the nominal ionopause with a vertical resolution of one O2+ scale height. • LPW shall measure electric field wave power • at frequencies important for ion heating. • Derived Level 3 measurement requirements:

11. EUV Measurement Requirements • EUV shall measure solar EUV input into upper atmosphere: • Solar EUV irradiance at wavelengths important for ionization, dissociation, and heating of the upper atmosphere with a time resolution sufficient to capture solar flares. • Derived Level 3 measurement requirements:

12. PFDPU Key L3 Requirements • PFDPU provides a single point interface for data and power between the PF Instruments and the Spacecraft (PF12,13,14,15,17) • No credible single point failure shall cause the loss of more than one instrument (PF11) • Common parts of PFDPU are redundant • No credible single point failure shall cause the loss of data from both MAG sensors (PF21) • PFDPU shall provide power switching for instruments and instrument attenuator actuators (PF15, 32, 33) • PFDPU shall perform instrument safing to protect PF instruments (PF42-49) • The PFDPU shall contain a relative time sequence engine containing sequences of commands to be run in response to mode change requests from the spacecraft, PFP fault management, or PFP measurements. (PF29) • PFDPU shall be capable of re-loading flight software on orbit (PF24,25)

13. PF Safing (ICD, PFDPU L3) • SEP detectors can overheat if exposed to continuous sunlight (>9 minutes at Mars) • Spacecraft Sun Avoidance protects instrument most of the time • SEP attenuator will protect detector when closed; close attenuator as part of SEP safing • PF instruments with High Voltage may be damaged (HV discharge) if operated during deep dips • SWEA, SWIA, STATIC • Manufacturer's data suggests worst case deep dip pressures may not be a problem; instrument level EM testing to confirm • Spacecraft to provide a pressure warning based on accelerometer data • PF instrument High Voltage will be shut off if thruster plume densities are expected to approach discharge levels • Spacecraft will attempt to place thrusters to avoid this • PFDPU to safe instruments in case of loss of communication with spacecraft • PFDPU to safe individual instruments in case of over-current or loss of communication • Spacecraft to safe PF in case of loss of communication or overcurrent

14. Accommodation Requirements (ICD) • STATIC Mounted to APP • Views RAM and NADIR during periapsis, pickup ion flows at higher altitudes • SWEA Boom-mounted • Mounted such that its 360 by 130 degree FOV has no more than 20% blockage by the spacecraft, and does not include the Sun when the spacecraft is in normal sun-pointing mode • SWIA Body mounted • Mounted such that it has a clear FOV in a 40 by 40 degree region centered on the Sunwards direction, extending in the spacecraft X-Z plane with at least 80% clear coverage around to anti-sunwards direction • SEP Body mounted • The two SEP sensors shall be mounted to provide maximum coverage of the Parker spiral field direction. The SEP FOV must be clear of any source of glint (i.e. nothing in the SEP FOV)

15. Accommodation Requirements (Cont.) • LPW Booms oriented such that: • at least one is outside the spacecraft ion wake and spacecraft shadow during science operations, and • the tip of each boom is at least 5m from the closest part of the spacecraft (including solar arrays and other appendages). • EUV body mounted • with a clear FOV of the Sun • MAG mounted on extensions at the end of the solar arrays • MAG shall be mounted far enough from the spacecraft body to meet the magnetics requirements. • The two sensors shall be mounted at sufficiently different locations to allow the spacecraft generated field to be modeled

16. PF Contamination Requirements (ICD) • PF contains contamination sensitive components • MCP, SSD, Thermal control surfaces, Optics • PF Contamination Control Requirements include: • Protective covers (in-flight and red-tag) • Class 100K clean room (or bagged) • Visibly clean (VCHS) exterior • High quality purge with limited outages • Post-launch contamination by thruster firing controlled by thruster placement, possibly closing apertures

17. Magnetics, Electrostatics, EMC • Magnetics Requirements (MRD) • The magnetic field at the Magnetometer sensors due to the spacecraft shall be less than 2nT DC, 0.25nT AC • Implemented via a Magnetics Control Plan, verified by component and system level tests. • Electrostatics (MRD) • All orbiter external surfaces shall meet the conductance and grounding requirements in the MAVEN Electrostatic Cleanliness (ESC) specification. • EMC (ERD) • LPW measures electric fields up to 2MHz • Sensitivity level included in the ERD EMC requirements

18. Spacecraft Interface (ICD) MAG 1 MFB Sec Vlt MAG Htr AD590 Prim Act ( TiNi ) MAG 2 Prim/Sec 28V TTL Prim Htr Act (NM) Sec Act ( TiNi ) T1 RS422 Analog Sec Htr 5V Discrete T2 Cage LPW 1 A1 A2 Boom A1 A2 Boom LPW 1 Sensor 3A LSw T1 T2 2A Ltch Sw T1 MAG Htr Elect T2 Cage 3A LSw LPW 2 A1 A2 Boom C&DH A1 A2 3A LSw (7) Boom DPU A LPW 2 Sensor USM1 Inst 1 Elect T1 T1 AAC T2 T2 EUVM H1 H1 H2 H2 No PDDU SPF T1 T1 T2 T2 SEP1 A1 H1 H1 will T1 T1 H2 H2 T2 T2 BP take H1 H1 H2 H2 T1 T1 SEP2 T2 T2 down A1 H1 H1 H2 H2 Mult DPU C&DH Instr T1 T1 STATIC T2 T2 2 B H1 H1 3A LSw (7) H2 H2 A1 A1 A2 A2 T1 T1 USM2 SWEA T2 T2 H1 H1 H2 H2 3A LSw A1 A1 2A Ltch Sw A2 A2 3A LSw T1 T1 PFDPU SWIA T2 T2 H1 H1 H2 H2 A1 A1 A2 A2 PIU PIM

19. PF Resource Requirements (ICD) Mass (PF9) Power (PF10) Telemetry (PF34)

20. PF Trade Studies in Progress • STATIC Redundancy • Determine if STATIC is mission critical, or can be backed up by other instrument measurements • If critical, determine what level of redundancy can be added • LPW Lyman Alpha Measurement • Determine how best to measure Lyman Alpha (LPW photocurrent or dedicated photodiode) • APP Pointing Optimization During ‘side orbits’ • Determine how best to point the APP between periapsis and apoapsis to allow STATIC to measure pickup ions and IUVS to make regional scans. • Deep Dip Pressure Sensitivity of HV instruments (SWEA, SWIA, STATIC) • Determine if we need to shut off HV during deep dips • Thruster Plume Sensitivity • Determine if we need to safe any instruments during thruster firing • Contamination, HV discharge concerns • Depends on thruster placement and plume analysis