Ronaldo Bellazzini (INFN–Pisa) Riunione Commissione Scientifica Nazionale II Frascati, 3 Ottobre...

Ronaldo Bellazzini (INFN–Pisa)[email protected]

Riunione Commissione Scientifica Nazionale II

Frascati, 3 Ottobre 2009

LAT Instrument Analysis and

Operations report

mailto:[email protected]

GLAST renamed Fermi by NASA on August 26, 2008

http://fermi.gsfc.nasa.gov/

“ Enrico Fermi (1901-1954) … was the first to suggest a viable mechanism for astrophysical particle acceleration. This work is the foundation for our understanding of many types of sources to be studied by the Fermi Gamma-ray Space Telescope, formerly known as GLAST. ”

“ Questo nuovo nome e' stato selezionato con un sondaggio pubblico realizzato dalla NASA e che ha ricevuto piu' di 12 mila risposte. Oltre ad avere un legame diretto con la scienza dei raggi-gamma della nostra nuova missione, Fermi ha un significato speciale per il DoE, l'ASI e l'INFN, tre agenzie che hanno maggiormente contribuito alla missione"

Jon Morse

Director of Astrophysics Division, NASA HQ, Washington DC

DoE – NASA – international partnership

LAT images the sky one photon at a time: -ray converts in LAT to an electron and a positron ; direction and energy of these particles tell us the direction and energy of the photon

GBM

June 11, 200812:05 pm (EDT)

GLAST Large Area Telescope GLAST First Light Seminar, 26 Aug 2008

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Circular orbit, 565 km altitude (96 min period), 25.6 degrees inclinationhttp://observatory.tamu.edu:8080/Trakker (track the satellite)http://www.nasa.gov/mission_pages/GLAST/news/glast_online.html (look at Fermi in the sky from your place)

Fermi in orbit

http://observatory.tamu.edu:8080/Trakker

http://www.nasa.gov/mission_pages/GLAST/news/glast_online.html

INFN-CSNII – October 3, 2008 Ronaldo Bellazzini

Major achievements since last yearMajor achievements since last year

• Launch on june 11!– 6 months delay in overall schedule for non-collaboration issues

– Had to move env test to NRL for conflict with another GD mission– 1 month delay at launch site for rocket issues

• An year full of successful training on simulations (OpsSim 1, 2, 3 and full sky simulations)

– Full development of data monitoring tools and data processing infrastructure

– Two generations of event analysis package (background rejection, event classes, IRFs) released and studied against simulations, third one in the works

– Most science analysis routines in place before launch• L&EO successfully completed

– Very smooth operation in all respect ( from S/C to event identification)– Functional and performance verification completed on schedule with

performance as expected– Nominal science configuration identified– Engineering data are effectively the first Fermi science data

• Routine science operations well under way– 2 full months of good data available and being analyzed– First set of papers ready for submission

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Year 1 Science Operations Timeline OverviewYear 1 Science Operations Timeline Overview

LAUNCH L+60 daysweek week week week month 12 m o n t h s

spacecraftturn-on checkout

LAT, GBMturn-on check out

“first light”whole sky

initial tuning/calibrations

pointed + sky survey tuning

Start Year 1 Science Ops

Start Year 2 Science Ops

in-depth instrument studies

sky survey + ~weekly GRB repoints + extraordinary TOOs

Release Flaring and Monitored Source Info

GBM and LAT GRB Alerts

continuousrelease of newphoton data

Observatoryrenaming

GI Cycle 1 Funds Release

Fellows Year 1Start LAT 6-month

high-confidencesource release, GSSC science tools advance release

GI Cycle 2Proposals LAT Year 1 photon

data release PLUSLAT Year 1 Catalogand Diffuse Model

2nd GLASTSymposium

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Commissioning highlightsCommissioning highlights

• Supported L&EO at SLAC with Duty scientists, Burst and Flare advocates, dedicated analysis– Instrument nominal configuration identified (trigger,

subsystem calibrations, timing)– Basic performance verified– Prescriptions for high level analysis outlined (data and

event selection)– Confirmation of expected results (EGRET) and discovery

science achieved• Transition to routine operations outlined

– Progressively more remote shifts (all kinds)– Automated tasks tested (ASP) and new tools under

finalization (RSP)– Improvement area in instrument analysis identified (Pass7)


Mapping of the SAAMapping of the SAA

The South Atlantic Anomaly (SAA) is a region with a high density of trapped particles (mostly low energy protons). We do not take physics data when in the SAA (ACD HV turned off), but we do count the TKR and CAL trigger to map the radiation intensity. Started with a conservative boundary definition, new polygon already uploaded on the spacecraft (time spent in the SAA reduced from ~18% to ~15%).


On orbit rates in nominal configurationOn orbit rates in nominal configuration

Overall trigger rate: ~few KHz Huge variations due to orbital effects.

Downlink rate: ~400—500 Hz ~90% from GAMMA filter ~20—30 Hz from DGN filter ~5 Hz from HIP filter

Rate of photons after the standard background rejection cuts for source study: ~1 Hz

Most of the downlinked events are in fact background, final ~ 1000:1 rejection is done in ground processing.


Tracker performance and calibrationTracker performance and calibration

No evidence of a reduction in hit efficiency (well above 99% on average) with respect to the ground calibrations. No significant change in the alignment constants (intra and inter-tower) after the launch (the LAT underwent up to 4 g acceleration). No evidence of any increase in the overall noise level (~1 noise hit per event for the full LAT).


Psf Validation with VelaPsf Validation with Vela

• Use Vela to validate PSF parameterisation– Take advantage of photon

phase to eliminate background

• Taking into account orbital variations– Compare direction error

distribution– Compare 68% containment

radius vs Energy


Instrument Response FunctionsInstrument Response Functions

• Release calendar– Pass4_v2 (correct energy

selection) on public performance page 7/2007

– Pass5 IRFs – sep 08 – Pass6 IRFs – may 08 –

current analysis and LAT paper

– Preparing to Pass7

Vela (2 cycles, P=89.3 ms) Geminga (2 cycles, P=237.1 ms)

PSR B1055-52 (2 cycles, P=197 ms)PSR B1706-44 (2 cycles, P=102.4 ms)

In a few days, Fermi confirmed the EGRET pulsars and found new -ray pulsars as well

Crab (2 cycles, P=33.4 ms)


PKS 1502-106 and 3C 454.3PKS 1502-106 and 3C 454.3

• The sky is dynamic, GLAST is monitoring the sky, catching flaring sources over different time scales.

• Atel #1628 (3C 454.3) and #1650 (PKS 1502-106) issued to announce these flares.


First GRBs detected by Fermi/LATFirst GRBs detected by Fermi/LAT

• 2 GeV GRB detected above 5 sigma, triggered by GBM– 080825C (GCN 8183) – weak burst– 080916C (GCN 8246) – many hundreds photons, exciting analysis in progress

080825C – LAT DATA 080916C – GBM DATA


Analysis systematicsAnalysis systematics

• Long-term strive• Many sources

– Instrumental effects (T, calibrations)– MC fidelity (geometry, physics processes)– IRF– Residual bkg modelling– Likelihood analysis

• Early papers conservative assessment – 30% on integral flux

– 5% trigger– 10% filter efficiency– 15% event selection cuts

– Residual background contamination critical for extended or faint sources, high energy regions – under verification


Future developmentsFuture developments

• Revised event analysis with lessons learned from LEO– Ghost track filter to minimize orbital effects

– Reject hits from track segments that did not fire single towers trigger

– Add ghosts to MC and produce training sample to test/update rejection

– New subsystems filters– New energy resolution and PSF sections– Revised background model

• Acceptance increase above 10GeV– CAL-only events

– Larger FOV at expense of angular resolution• Augmented particle identification

– Electron tagging with classification techniques– Protons and nuclei tagging


MC validation from CERN Beam TestMC validation from CERN Beam Test

From the LAT paper – 45° incoming angle, 5.3% global scaling factor applied to MC

Major Updates

• T effects on CAL corrected• Discovered G4 bug in LPM implementation thanks to shower fine sampling, now available in Geant4 9.2-beta-01

Major improvements

• CAL energy scale in good agreement with a single recalibration factor• basic TKR and CAL variables in agreements• shower transverse size in CAL still not properly reproduced in MC


GLAST LAT ScienceGLAST LAT Science

• Science Working Groups– Calibration and Analysis Methods (L.Latronico, P,Bruel)

– Beam Test (Latronico, Bruel)– IRF development (Rando), IRF monitoring (Cecchi)

– Blazars and other AGNs (G.Tosti, B.Lott)– Diffuse and Molecular Clouds (T.Porter, A. Strong)– Catalogs (D.Thompson, I.Grenier)– Pulsars, SNR and Plerions (D.Smith, A.Harding)– GRB (N.Omodei, V.Connaughton)– Sources in the Solar System (F.Longo, I. Moskalenko)– Dark Matter and new physics (J.Conrad, R.Johnson) (just rotated A.Morselli, E.Bloom)

• Satellite groups – Multiwavelength – GeV-TeV connection

• Analysis coordination– Julie McEnergy, Nicola Omodei (deputy)


Papers in the pipelinePapers in the pipeline

• In preparation (Category 1):– 3C 454.3 (Tosti*…)– 1st new pulsars (from known ephemerides) (…Caliandro, Gargano,

Razzano…)– Pulsar catalog (Caliandro*…)– Vela 1 Pulsar (Razzano*…)– Other papers are coming shortly…

• Ready for submission (Category 2):– Prospects for GRB science with the GLAST Large Area Telescope

(Omodei, Longo, Baldini…) – Pulsar Simulations for LAT (Razzano,…)– “LAT instrumental paper”

• Submitted:– Discovery of a new gamma-ray pulsar… (blind search)


ConclusionsConclusions

• Fermi-LAT is fully operational since june 25 and in routine survey mode since august 11 (end of commissioning)

• The commissioning phase was extremely smooth and satisfactory thanks to the thourough preparatory work of the full collaboration

• A new observational window in the Universe has opened– EGRET/AGILE results corroborated in just a few days– Exciting new discoveries coming up soon

• INFN is a key-player in this story of success since the beginning of the project– TKR construction and qualification– Instrument calibration– Science analysis

Ronaldo Bellazzini (INFN–Pisa) Riunione Commissione Scientifica Nazionale II Frascati, 3 Ottobre...

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