FDMO Peer Review RFA Summary

FDMO Peer Review RFAs RFA Title Rationale Reviewer Response Status Investigate monthly lunar perturbation effects to determine optimal time during month to launch. Lunar perturbations can be used to reduce fuel required if judicious selection of launch date is made. However, lunar perturbations can also increase fuel required by decreasing orbit energy & negatively impacting orbit inclination. Richon The THEMIS team has already built tools which allowed investigation of lunar perturbations on orbits P1, P2 and P3 as well as on the LV insertion orbit in order to minimize potential for re-entry on the science orbits, and to maximize the potential for re-entry within 10 years for the LV to adhere to orbital debris requirements. Lunar effects due to different launch dates on the P3, P4 and P5 orbits were found to be very small. CLOSED FDMO-2 Decide on one pre-injection nomenclature for each probe. Should not be names associated with integers 1-5 since the probes will be numbered Probe 1, Probe 2, etc. post-launch according to their final orbit positions (similar to TDRSS). Currently probes are designated as “Themis 1, Themis-2,…”, “red,green…”, and “A,BC…”. Multiple names for same probe causes confusion & misidentification of specific probes. The team agreed that the pre-launch assignment of probe names shall be THEMIS A-E. These names are uniquely related to the CCSDS telemetry and command IDs for each probe bus. Probe constellation IDs P1-P5 are assigned post-launch, once the probes and their instruments have been checked out and the probe placement decision has been made. FDMO-3 Resolve time tag issue. Harman The THEMIS attitude sensor read-out timing and attitude determination system is modeled after the FAST system which has been operational for almost 8 years.

FDMO Peer Review RFAs RFA Title Rationale Reviewer Response Status Get initial 3rd-stage separation states (attitude & orbit) for each probe from Boeing. Needed for orbit injection analysis. If Delta PMA is being done, these states should be available soon. Richon UCB received the nominal launch trajectory ephemeris from KSC. These data are used to perform subsequent studies such as communications coverage and probe re-contact analyses. CLOSED FDMO-5 GMAN modeling issues: define each ‘maneuver mode’ including type of maneuver, which thrusters used, pulsed/continuous, etc. Then determine if GMAN can model maneuver correctly. Several questions regarding whether GMAN can be used to model finite maneuvers in all maneuver configurations. All anticipated orbit and attitude maneuvers have been summarized and analyzed. Bob DeFazio verified that all maneuvers can be modeled with GMAN. FDMO-6 Determine ground station contact tracking requirements such as pass frequency & duration, number of stations, for maneuver planning & recovery versus regular OD, etc. Mark Beckman performed an OD covariance analysis that shows what number of passes and arc lengths are required to meet THEMIS OD requirements. FDMO-7 Determine UCB station capabilities including support for perigee passes. Mission depends heavily on UCB antenna for tracking. Need to know if orbit determination constraints can be met. Two-way Doppler tracking capabilities of BGS demonstrated with equipment on loan from Wallops Flight Facility. Expected 1-sigma error of range rate measurements is expected to be 3.5 mm/s in 10-s integration time. Due to the low orbital inclination the maximum azimuth and elevation rates will be less than 0.2 deg/s.

FDMO Peer Review RFAs RFA Title Rationale Reviewer Response Status ITOS-to-MSASS interface code to be provided to UCB. Harman used successfully for other mission. Richon UCB will provide interface code to extract attitude sensor data from ITOS and reformat these to be compatible with MSASS/MTASS input. CLOSED FDMO-9 Real-time attitude determination - is this a requirement? If so, which software? Possibly use MTASS with modifications. Harman Real-time attitude determination is required for maneuver support. A ground-based real-time ADS will be implemented, based upon the quaternions that are derived from sun sensor and IRU data and are propagated on-board. FDMO-10 Multi-satellite critical operations: need to have at least two prime workstations supporting, plus at least one hot back-up for emergencies. Normally one has one prime and one back-up for any critical operation for a single-satellite mission. UCB will have to be able to support multiple satellites with critical operations. The ground systems design includes at least 10 ITOS workstations, including a designated prime and back-up for each probe. Furthermore, any of these workstations can be assigned to any probe. In addition, two ITOS workstations will be connected to the Closed IONet for communications via TDRSS. FDMO-11 MSASS is not capable of performing magnetometer alignment. Determine if UCB needs to acquire MTASS in addition to MSASS for this function. UCB will obtain ADS which includes both MSASS and MTASS. A software usage agreement is in the process of being finalized.

FDMO Peer Review RFAs RFA Title Rationale Reviewer Response Status Include pre-launch operations (Simulation planning & support, launch preparations) in future FD&MO reviews. Ensure resource requirements are identified & included in planning. Richon Pre-launch operations and simulations including green card exercises were already included in the MPDR presentations. CLOSED FDMO-13 Provide access to latest mission information to peer panel at least two weeks before review. The review team will receive most recent mission documentation at least two weeks prior to future peer reviews. FDMO-14 Maneuver calibration procedures need to be documented. Each orbit & attitude maneuver should be analyzed post-maneuver for efficiency & accuracy. Results should be applied to future maneuver planning. Also needed for bookkeeping of fuel used. The UCB team has received sample procedures from GSFC FDAB and from Swales for EO-1 maneuver planning and execution. Appropriate elements of these procedures will be incorporated into the THEMIS procedures. FDMO-15 Document who is responsible for fuel-used bookkeeping (propulsion engineer or Flight Dynamics Engineer or other FOT member). One entity should have responsibility for this function. It is particularly critical at the end of life when probes must perform a controlled reentry. A dedicated member of the THEMIS flight dynamics team, i.e. the propulsion engineer, will be responsible for bookkeeping the fuel usage.

FDMO Peer Review RFAs RFA Title Rationale Reviewer Response Status Institute Command Authorization Meetings (CAMs) for all orbit & attitude maneuvers. Requires participation & ‘signoff’ from all relevant subsystems & systems (FOT, flight dynamics, thermal, power, C&DH, scientists, etc.). Best practices. Reduces risk. Richon Command Authorization Meetings (CAMs) will be held prior to any critical command operation, including execution of orbit and attitude maneuvers as well as critical instrument operations such as boom deployment or HV turn-on. Such meetings are common practice with all missions currently operated by UCB. CLOSED FDMO-17 Provide MAP Anomalous Forces technical paper to UCB. Outgassing of instruments & other hardware may introduce anomalous forces creating torques on probes). UCB received a copy of the MAP anomalous force paper. FDMO-18 Provide JON/WBS to Code 595 for THEMIS support. Code 595 flight dynamics engineers cannot support THEMIS without charge number. Angelopoulos & Richon GNCD has received a JON for support of THEMIS flight dynamics support.