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Fermi Fermi Gamma-ray Space TelescopeGamma-ray Space Telescope

Users Group MeetingUsers Group Meeting20 July, 201220 July, 2012

Mission Status UpdateMission Status Update

J. McEneryJ. McEnery

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Some goals for this meetingSome goals for this meeting

• Comments and feedback from the users group on:– VERITAS in Fermi GI program– Observation strategies in extended phase of the mission –

providing an opportunity for people to make ambitious suggestions

– Senior review – suggestions on how to improve the process next time

– Evaluating the performance/effectiveness of the GI program– How to better enable users – software, documentation, MW

resources, operations information etc

• Of course, comments on suggestions on any aspect of the mission are welcomed!

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Mission Status HighlightsMission Status Highlights

• Observatory is operating smoothly– Closely monitor reaction wheels - no issues or concerns.

• Reaction wheel life complete, analysis/evaluation almost complete

• Updated FSW to handle reduced wheel observation modes - code completed and tested.

– Collision avoidance maneuver (see later slides)– Coarse sun sensors – no problems after solar TOO

– Sunpoint/safehold on Oct 21, 2011 after exiting nadir observation

– Sunpoint/safehold on Feb 6, 2012 during GNC testing• Fermi sessions at AAS, AAAS and COSPAR• Many data/software updates• Senior Review (proposal, presentation and post-review budgets)• 8 NASA press/web releases, several other press releases from

other institutions

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Observations summary (since last Observations summary (since last meeting)meeting)

• Almost exclusively in nominal data taking in survey mode• ARRs (1-2 per month)

– Duration of each ARR is 2.5 hours

– 4 TOO

– Sun, Crab x 2, Galactic Center

• 1 modified survey mode observation– Stay south for sun observations

– 25 nadir observations– Modified LAT and GBM configurations during these

observations• LAT Calibrations/engineering tests

– <24 hours

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Conjunction assessment reportsConjunction assessment reports

• Routine daily screening• Detailed information provided for any object predicted to come

within a box 0.5km x 10km x 10km (radial, along track, cross track), the CARA team process this data and provide us with a summary:– Time of closest approach– Miss distance in each direction– Probability of a collision (assuming a 20 m spacecraft radius)– Overall risk metric

• If Owner/Operator (O/O) ephemeris available, two conjunction predictions are supplied:– “ASW”: uses orbit determination performed at JSpOC for Fermi

– “O/O”: uses mission-provided ephemeris for Fermi (derived by the flight operations team from the GPS data)

• If a high risk event is identified, then we request additional screenings (up to 3 per day)

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Fermi vs Cosmos 1805Fermi vs Cosmos 1805

FGST (33053) Apogee Height:561 km Perigee Height:552 km Inclination:25.6°Cosmos 1805 (17191) Apogee Height:599 km Perigee Height:563 km Inclination: 82.5°Conjunction Location: Latitude:10.6° N Longitude:115.5° ERelative Velocity:12.1 km/sApproach Angle:105.8°

FGST

Cosmos 1805

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Conjunction visualizationConjunction visualization

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Terrestrial Gamma ray Flashes (TGFs)Terrestrial Gamma ray Flashes (TGFs)

Electrons, Positrons

– Thunderstorms produce intense sub-ms -ray flashes• Power in flash of MeV -rays is comparable to power in lightning bolt

– Thunderstorms are the most powerful natural, terrestrial particle accelerators

• Key questions– Relationship to lightning?

• Which storms? Which types of lightning? Which stage in lightning process?

– What is the physics of the accelerator? Where is it?

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Observational ProgramObservational Program

• Nadir observing– LAT has 13x physical area, deeper calorimeter, and ~10x shorter imaging

deadtime than AGILE• Put TGFs into LAT aperture to have sensitive test for >100 MeV -rays

– Reorient to observe nadir over thunderstorm regions• Central America has highest density of historical TGFs• TGF activity correlated with thunderstorm activity

– Must observe in late afternoon (local time) through night

– Optimize LAT configuration for fast, bright transients• Turn off on-board GAMMA filter to ensure all events are telemetered• To limit data volume, disallow trigger types for >10 GeV gammas and

heavy cosmic rays

76-P097-13 9

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Sunpoint and Nadir ObservationsSunpoint and Nadir Observations

• During nadir observations the star trackers are blocked by the Earth– Attitude solution is propagated for an extended period

using the gyros alone– Disable safehold check that requires that we don’t go

more than 20 mins without star tracker lock– Re-enable safehold check at end of Nadir run

• Nadir obs #13– The gyro based solution had sufficiently diverged over the nadir

observation such that the trackers (fed by GNC) were unable to lock onto enough stars to provide the new fine point solution.

– Re-enabled safehold check expired and Fermi entered sunpoint

• Began sequence of tests

– Disable star trackers during slew between +- 50 deg rocking

– Examine performance when re-engaging star trackers

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Test #3 and conclusionsTest #3 and conclusions

• Large residuals after first 2 hours of test meant that STs lost lock and were unable to regain lock within 20 mins– another safehold/sunpoint

• Conclusion:– A random disturbance/deviation at the last ST update can cause

the KF attitude solution to have large drifts• In non-standard survey modes (nadir, limb) the gyros are in a

different thermal environment– Current specs do not guarantee that the observatory attitude is

accurate to <10 deg after 1 orbit in nadir obs • Very small possibility that the observatory could cease to be

power-positive during long duration non-standard observations

• We cannot guarantee safe exit from nadir observations, need to staff MOC for nadir obs

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Observations planningObservations planning

• The Science Policy Document (linked from the main Fermi users group page) describes the current policy for balance of observation modes– >70% sky survey + ARR

• ARR rate is lower than originally planned, duration now shortened

– <= 20% pointed mode, planned TOO, Nadir observations• None in cycles 1,2 and 3; nadir observations in cycle 4

– <= 10% Mission discretionary time - MDT (unplanned TOO, time critical science observations between GI cycles, calibrations)

• Crab, sun and Cyg-X3 TOOs; sun modified survey mode• Small amount of calibrations/engineering <1 day/year• Reported to FUG

• Unused pointed mode and MDT allocation is assigned to sky survey.

• It was anticipated that we may want to increase the allocation of pointed mode later in the mission – need to provide a forum for community suggestions etc

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long duration non-standard survey mode long duration non-standard survey mode observations – a possibilityobservations – a possibility

• Solicit white papers on new observation strategies/ideas– Long pointed mode observations– Significantly modified survey strategies

• Provide technical assistance and updated documentation on observatory capabilities and constraints

• Form panel to review the white papers and provide a recommendation to the Fermi project

• Possible timeline– January 2013: issue call for white papers– May 2013: submission deadline– June 2013: review

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Fermi Solar Data Analysis WorkshopFermi Solar Data Analysis WorkshopAug 22-23 at GSFCAug 22-23 at GSFC

• Fermi as a gamma-ray Solar Observatory?– GBM regularly detects solar flares– LAT detects both the quiescent

sun and flares in survey mode• Solar physics and astrophysics

communities have different methods for data access and analysis

• Fermi data is seen as inaccessible to Solar community (mitigated somewhat by GI program on SSW/OSPEX PI: Dennis)

http://apod.nasa.gov/apod/ap120315.html

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Fermi Solar Data Analysis WorkshopFermi Solar Data Analysis WorkshopAug 22-23 at GSFCAug 22-23 at GSFC

• Solution: Get everyone in the same room and open to both the solar physics community and Fermi users– Teach how to analyze GBM data in SSW/OSPEX as well as GBM

teams RMFIT software– Teach the Fermi Science Tools analysis and new LLE data, with

joint LLE/GBM fits in XSPEC– Do all of this with the software developers physically in the same

room– Requiring creative solutions to software challenges (virtual

machine environment)– Currently >40 people registered for workshop from around the

world• Hopefully encourage new collaborations and make contacts

between communities

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Workshops and SchoolsWorkshops and Schools

• Should we focus more on topic-specific workshops?

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44thth Fermi Symposium Fermi Symposium

Oct 28 – Nov 2, 2012 in Monterey, California

http://fermi.gsfc.nasa.gov/science/symposium/2012/

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• Fermi is a young mission!– The community

of Fermi users is growing by 10-20% per year

– Analysis gets more complex and difficult with time

– User support workload continues to grow

Increasing User Support NeedsIncreasing User Support Needs

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Note: These represent US Fermi users only

“…we have yet to see the peak of Fermi’s science output” -- 2012 Senior Review

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Growing Science ProductivityGrowing Science ProductivityGrowing Science ProductivityGrowing Science Productivity

– Rate of Publications and PhD theses continue to rise

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Fermi BibliographyFermi Bibliography

• http://fermi.gsfc.nasa.gov/cgi-bin/bibliography_fermi

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Complex instrument● Very large number of LAT signal channels (>800,000 tracker, ~6000

calorimeter) Monitoring nontrivial

● Calibration requires expertise across the team to create, test, implement, update user software, and deliver updates

Regular updates necessary to counter expected degradation High rate and volume of data

● Promptly addressing issues in data acquisition, downlink and transfer, and processing reduces latency and risk of permanent loss

Low latency critical for time domain science Broad analysis needs and user community

● Most users initially unfamiliar and benefit substantially from help beyond documentation to address specific analysis needs

Fermi science is extremely broad!

● Users from several communities● New analysis needs generate development within team that

propagates to community through SSC Science breadth in SSC makes this more efficient

Fermi Mission Complexity

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AcknowledgementsAcknowledgements

• Contributions and help from many many people (too many names to list)– Science write ups– Review of proposal and presentation

• Special thanks to Seth Digel, Judy Racusin and Dave Thompson who wrote the proposal and to Alan Marscher as the co-presenter

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Questions?Questions?