Fermi Gamma-ray Space Telescope

Mission Parameters

Parameter Requirement Goal
Lifetime (< 20% degredation)1 > 5 yrs > 10 yrs
Telemetry Downlink:
Orbit Average
Realtime2		  
> 300 kbps
> 1 kbps		  
> 1 Mbps
> 2 kbps
Telemetry Uplink - Realtime2 > 1 kbpsr > 2 kbps
Time to Respond to TOO's on Ground3 < 6 hours < 4 hours
Spacecraft Repointing
Times for Autonomous Slews4		 < 10 min < 5 min
GRB Notification Time to Ground by Spacecraft5 < 5 sec < 2 sec
Pointing Accuracy (Absolute)6 < 2° < 0.5°
Pointing Knowledge6 < 5 arcsec < 2 arcsec
Observing Modes - Rocking zenith pointing
- Pointed mode7		  
Targeting No restrictions on pointing
of axis normal to LAT		  
Uniformity of Sky Coverage during Scanning8 < ± 20% < ± 10%
Observatory Absolute TIme Accuracy9 < 10 μsec < 3 μsec
Observatory Absolute Position Accuracy < 3.3 km < 1 km
Observing Efficiency10 > 90% > 95%
Data Loss11 < 2% < 1%
Data Corruption12 < 10-10 < 3 x 10-11

1 20% degradation = no more than 20% loss of LAT science return
2 Uplink telemetry rate for at least 80% of time outside of SAA
3 Response time for the MOC to uplink a spacecraft repointing after the decision is made to respond to a Target of Opportunity (TOO).
4 Time for 70 degree slew.
5 Time from spacecraft receipt of GRB notification from GBM or LAT to delivery to the Gamma-ray Coordinates Network (GCN) computer for 95% of all GRBs detected by the GBM or LAT.
6 1 sigma radius
7 Pointing of axis normal to LAT to within 30 degrees of source. (No science constraints on roll axis.)
8 Sky coverage exposure uniformity integrating for 7 days, not including SAA effects.
9 Relative to Universal Time, 1 sigma r.m.s.
10 Fraction of time taken with data return, not including SAA effects.
11 Fraction of data taken by the instruments but not delivered to the IOC. Not including SAA data loss. Not including instrument deadtime.
12 Fraction of undetected corrupted events.