Fermi Gamma-ray Space Telescope

Fermi ToO 030604-1-1

A ToO observation to observe CRAB at RA, Dec = 83.6330, 12.0140 (J2000) was approved at 2011-04-12 15:49:44 UTC.

The justification for the ToO is: LAT measurements indicate the Crab Nebula is entering a new GeV flare state. The flux is currently comparable to previous flares. The level of activity visible in the public source lightcurves has only been seen previously in association with close Sun passages and the LAT flares in Feb 2009 and Sept 2010. Offline analysis confirms the enhanced flux. The Sun is currently about 60 deg away from the Crab. The synchrotron portion of the Crab spectrum evolved during the Sept 2010 event. The highest energy synchrotron photons from a Crab flare are critical test of the flare mechanism. There is a significant advantage to a TOO observation, which will enhance the exposure by a factor of 2-3X. A previous ToO began as the flare ended and so we encourage rapid scheduling if this request is approved.

The planned duration is 300.00 ks.

The autonomous request threshold during this ToO is LOW.

The ToO observation should begin between 2011-04-12 15:49:43 UTC and 2011-04-19 15:49:43 UTC.

The ToO observation was requested by DR. ELIZABETH HAYS.

The ToO commanding order was sent to the MOC at 2011-04-12 16:25:16 UTC.

The MOC acknowledged receipt of this order at 2011-04-12 16:26:23 UTC.

The MOC sent the ToO execution notification at 2011-04-12 18:30:31 UTC.

The ToO order status is Uplinked: Command accepted by the spacecraft at 2011-102-16:47:22