Next: Maximum number of subscans
Up: Mapping
Previous: EKH vs shiftandadd restoration
Contents
When mapping, the noise per independent resolution element in the map
(
) is given by

(23) 
where
is the total integration time per independent resolution
element,
is the number of repeated coverages and
is
the number of independent resolution elements per bolometer of the
array. This number is easily obtained through

(24) 
where
is the total number of valid bolometers (equal to the
maximum number of bolometers minus the number of dead ones),
is
the solid angle of the resolution element in the map (assumed to be a
Gaussian),
is the factor due to gridding and
is the
telescope full width at half maximum. Using the equations derived from the
mapping strategy, it is easy to obtain

(25) 
In the case of MAMBO,

(26) 
However, this noise value stands before any data processing. The
restoration will multiply the above noise level by the square root of the
number of chopper throws used to compute the brightness at any given
position. This makes the actual noise value dependent on the total map size
in the scanning direction. Moreover, the methods to restore the source are
not perfect^{1}. Altogether, we thus use

(27) 
where
value is deduced from the experience of the
previous bolometer pools with MAMBO at the IRAM30m.
Next: Maximum number of subscans
Up: Mapping
Previous: EKH vs shiftandadd restoration
Contents
Gildas manager
20140701