Orbit Mode observation Technique Developed for VERITAS

Understand

The canonical observation mode for IACT gamma-ray observations employs four discrete pointings in the cardinal directions (the "wobble" mode).

• For the VERITAS Observatory, the target source is offset by 0.5-0.7 degrees from the camera center, and the observation lasts 20 minutes.
• During January/February of 2011, the VERITAS Observatory tested a new "orbit" observation mode, where the target source is continuously rotated around the camera center at a fixed radial offset and constant angular velocity.
• This mode of observation may help better estimate the cosmic ray background across the field of view, and will also reduce detector dead-time between the discrete 20 minute runs.