1. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status 1
The previously discussed support by GSFC to train UCB/THEMIS personnel in the use of GTDS for end-to-end orbit determination operations has not been implemented. This training is vital to the development of this key mission function.
1. An agreement between appropriate GSFC and UCB/THEMIS personnel should document the required orbit determination training and the technical personnel to support the training.
2. A training plan as part of an overall orbit determination operations schedule is to be provided one month prior to MOR.
Joyce
OPEN 2
There may be no documented requirement that an updated post-injection vector be provided to the THEMIS Project based on Boeing Delta Redundant Inertial Measurement System data. This data is required to maintain communications with the probes until an accurate orbit determination is available. It is even more important in the event of a non-nominal injection.
The Project should pursue levying this requirement with additional details provided by GSFC/FDF on Boeing prior to the MOR.

2. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status 3
Currently, the mission design work centers on the evolution of Keplerian elements. However, it has been claimed that despite their individual motions the line of apsides of each orbit remains constant for 1st order.
A set of plots showing the right ascension and declination of the line of apsides is suggested to support this claim and to clarify the reasons for selecting a constant RAP.
Schiff
OPEN 4
A delta V budget with allocations to account for daily / time-of-day launch window and ELV dispersions was not presented and may not be available as of this date. A complete delta V budget is needed to determine how stable the current design is.
A technical approach and schedule should be drafted as soon as possible and be submitted for a review at MOR. 5
On Slide 7 of the Propellant Budget, four delta V inefficiencies were considered. However, these inefficiencies are all associated with the geometry of the thruster, either in the body frame (i.e. misalignment) or inertially (rotational impulse loss sin(η/2) / (η/2), the beta inefficiency, and finite arc losses). However, performance loss is not considered.
The project should take a specific position on an Isp inefficiency which, if considered, will lower the overall ΔV capability of the spacecraft. Consider the rocket equation:
ΔV = g Isp ln (mi / mf)
A change in Isp of δIsp will cause a change in ΔV. If the Project decides against considering this possible inefficiency then they should be clear on all ΔV budgets that such an inefficiency is not being used.

3. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status 6
Clarify requirements in mission for close approach/debris per NASA Safety Standard and NASA Policy Directive B. NASA satellites are required to provide predicted ephemeris to Cheyenne Mountain for every orbit-changing maneuver of >1 km, and for launch and early orbit operations.
Review NSS & NPD B to determine requirements applicable to THEMIS. Incorporate into procedures and analysis.
Richon
Requirements for close approach and orbital debris generation are addressed in the THEMIS Final Orbital Debris Report (CDRL #37) which was submitted by the Project for review by NASA HQ, GSFC and KSC. UCB will work with Adrienne Davis at GSFC/FDF to prepare the required paperwork to notify DoD about THEMIS orbit maneuvers in accordance with NPD B, Section 5.b.7. Notification of DoD will be part of the operations procedures.
OPEN 7
Need verification / QC of trajectory design and maneuver plan for all probes. Currently one person (Frey) doing all analysis.
Need capability for targeting and optimizing trajectory design. FreeFlyer (AI Solutions) can do this.
Contract with GSFC, AI Solutions, other trajectory design group to verify trajectory design and maneuver plan. If switch from GMAN to FreeFlyer, AI Solutions is logical choice.
A consulting contract will be set up between UCB and AI Solutions to verify GMAN/FreeFlyer compatibility. If compatible, UCB will purchase a FreeFlyer Engineer run-time license. AI Solutions may be contracted by the Explorer’s Office to verify the mission design. 8
There is a requirement for use of MSASS and MTASS for attitude determination. As of now, there is no formal agreement between GSFC/FDAB for any requirement or modifications to software, delivery of software, version (CM) for software, or testing to meet launch schedule.
Agreement on requirements for software, delivery schedules, versions and testing needs to be done as soon as possible with GSFC/FDAB. Resource (funding) to make any modifications or do testing needs to be agreed upon.
Hoge

4. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status 9
Version of GTDS software is planned for upgrade to latest version. GSFC/FDF maintains only an HP version of software. A Solaris version is used for THEMIS operations and analysis. When updated version is delivered will need to be compiled under Solaris. This will require time and resources to compile and test software that may not be in schedule. Additionally, CM process for upgrade is not clear.
Determine effort for testing and verification of software. Implement a CM process for GTDS software if one does not exist. Work with GSFC/FDF for software upgrade via Commercialization Office at GSFC.
Hoge
OPEN 10
Given flexibility and priority of data available from day to day of the mission, is there a science data collection statistic that can be agreed upon as a measure of mission success?
Identify statistics and metric and include in operations plan to monitor performance.
Crouse
Conjunction science data up to 750 Mbits per orbit collected during the wedding season (February 21 ± 2 months) and during the dayside season (August 21 ± 2 months) are considered mission critical, and 100% recovery will be attempted. In addition, up to 40 Mbits of data collected in slow survey mode during radiation belt crossings of each orbit are to be recovered at the 100% level also. Also, all probe state-of-health and engineering data are to be recovered at the 100% level. Other data are of lesser importance. Statistics will be generated against the above metrics.

5. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status 11
Understand implications (if any) of the NISN mission operations voice enhancement activity.
Review Project Management Plan from NISN and identify impact (schedule, cost, etc.).
Crouse
THEMIS Network Operations Manager (John Ervin) states there is no problem with UCB’s SCAMA system w.r.t. planned voice system upgrades at GSFC.
OPEN 12
Current analysis uses 50% penumbra to determine eclipse. What impact is there for penumbra less than 50% on both power and thermal?
Look at eclipses defined as 100% (umbra) from beginning of penumbra to end of penumbra. Evaluate recharge period as well. 13
Are maneuvers needed specifically to calibrate the gyros? Will maneuvers already in the orbit plan be enough to calibrate the gyros?
A study is needed to see if the gyros can be calibrated sufficiently through the nominal course of maneuvers. Is there enough observability of the attitude about these maneuvers plus enough maneuvering about different axes? Can bias, scale factor and misalignment be solved? If there are errors in these, how much attitude error will there be and will this be more than the knowledge requirement for maneuvers?
Ottenstein 14
The health-and-safety check of THEMIS B is currently scheduled during shadow without any check before ATS load in sunlight.
Insert a 10-minute delay in BGS acquisition health-and-safety checks so all five probes are in sunlight.
A delay was inserted into the L&EO timeline so that all probes are in sunlight during the first BGS pass set.

6. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status 15
It appears that more attitude analysis is needed to prepare for the mission. The presentation does not show enough analysis yet.
1, Derived requirements. Are there thermal or instrument constraints which will derive requirements on attitude determination or control? Are there Sun angles to be avoided? Consider the problem of the EFI on POLAR at certain Sun angles and determine whether such a problem will apply to THEMIS. Determine what the range of Sun angles is during the mission.
2. Torque analysis. How much change to gravity gradient, solar radiation pressure and dipole moment torques affect the attitude and Sun angle per orbit and over the course of a month?
3. Nutation damping. How quickly will nutation be damped after a maneuver and separation? If it does not damp as expected, are there contingency plans to actively damp it?
Ottenstein
OPEN

7. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status
4. Shadow analysis. How will long shadow periods affect the attitude of the spacecraft? Will there be perturbations to contraction of the booms? How will the shadows affect the ability to perform attitude determination? Are maneuvers planned with respect to knowledge of the shadows? How are gyros affected? How is the system affected by not having a Sun pulse during the shadows? Data from WIND, POLAR and FAST of spin rate changes near eclipse may be of use.
5. Attitude error budget. How was the 1% science error budget obtained? How stringent is it? What elements of error go into the budget?
6. MSASS training. If a copy of MSASS using Sun and FGM is available before the version with the Kalman filter, this should be used with FAST data to see how well Sun and magnetometer agree with Sun and Earth for training with use of FGM data.

8. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status
7. MSASS studies. At each planned attitude examine observability for Sun sensor and magnetometer. Generate simulated data (Matlab can probably generate this to go directly to the DA system). One group should generate the data while another group should determine the attitude with an a priori knowledge of no better than 5 deg or so. Generate clean data first, but at proper bin size, then later include noise and misalignments and offsets that can be expected.
8. Magnetometer observations are critically affected by timing errors. How will offsets in time be communicated to the attitude determination team? Will additional MSASS development be needed? Note that analysis with Matlab for magnetometer only attitude solutions for a spinning spacecraft (FAST and IMAGE) was made for GSFC in the past and these studies should be examined.

9. FDMO CDR Peer Review RFAs
Statement of Concern
Recommended Action
Reviewer
Response
Status 16
TDRSS SSA support is baselined. TDRS HIJ SMA services may be able to support telemetry and command and have greater availability.
UCB/SSL should investigate use of SMA services from TDRS HIJ and that Doppler rates at perigee passes are within TDRSS limits.
Gramling
Code 450 performed a link analysis for TDRSS, showing that only TDRSS SSA mode is feasible. In addition, the GN style THEMIS transponder is not compatible with SMA mode in terms of modulation and frequency.
The maximum range rates between the THEMIS probes and TDRSS are 10.5 km/s and 2.4 m/s2 near perigee of the insertion orbit. The maximum rates that TDRSS can support are 12.0 km/s and 15.0 m/s2, respectively.
OPEN 17
There may not be sufficient tracking data (from more than one station) to allow for post-launch orbit determination (may not have adequate acquisition data). There may be a time gap in the timeline at 02:15 to 03:50 MET where another ground station, preferably Santiago, to get two-way Doppler data. Or, can second set of round-robins (starting at 04:00 MET) be done through another ground station?
Look at timeline to see if another station could be brought up to get additional Doppler data sooner after launch. Develop timeline for early orbit solution updates and determine OD support and station requirements. Timeline should go through the first apogee maneuvers (perigee raising) for all five probes and include time after maneuvers to do OD. 18
Is there a requirement for a back-up MOC?
If yes, pre-launch testing would be required.
Hoge
No (Frank Snow).
CLOSED