Imaging Burstmode

Starting with Period 80, the burst readout is offered for the imager in visitor mode only. The burst readout allows the user to save every single DIT frame of an exposure. In this way it is possible to follow rapidly evolving events or to improve the spatial resolution by taking short enough exposures to freeze atmospheric turbulence. This mode can be used only for objects that are bright enough to provide a S/N high enough in a single elementary frame. Typical flux limits are of the order of 5 Jy in the N band and 10 Jy in the Q band. Some compromise between sensitivity and time resolution can be reached by averaging a number of elementary frames.

A detailed description of the burst mode and its application to a typical science case is given in Doucet et al. (in press; proceeding of "Visions for Infrared Astronomy", held in Paris, 20-22 March 2006).

To estimate the sensitivity in burstmode with ETC, the user is asked to use the following table which gives for each filter the DIT setting in SF / IF imaging assuming the default weather flag = Good.

Imaging Filter DIT setting (SF / IF)

[ms]

for weather flag = Good

PAH1 20.0    /    62.5
ArIII 62.5    /    20.0
SIV_1 10.0    /    25.0
SIV 40.0    /    16.0
SIV_2 16.0    /    50.0
PAH2 10.0    /    40.0
SiC 25.0    /    10.0
PAH2_2 12.5    /    40.0
NeII_1 20.0    /    62.5
NeII 25.0    /    80.0
NeII_2 20.0    /    62.5
Q1 40.0    /    12.5
Q2 40.0    /    12.5
Q3 12.5    /    40.0