Geoscience Reference
In-Depth Information
to photon statistics. As a consequence when one measures a given signal
width, due to the intrinsic uncertainty of the measurement due to photon
noise, there is a corresponding range of angular sizes which are compatible
with the measured signal width. This uncertainty is obviously increasing
for decreasing signal intensity, or in other words for decreasing apparent
brightness.
The complex interplay of magnitude (signal intensity), apparent angu-
lar size and resulting signal width has been explored by means of extensive
numerical simulations. According to preliminary results, one can separate
the apparent magnitude — apparent angular size plane into two distinct
domains, according to the possibility to derive an angular size measurement
having a relative accuracy better or worse than 10%, as shown in Fig. 2.
140
better than 10 %
120
100
80
60
40
worse than 10 %
20
0
12
13
14
15
16
17
18
19
20
M (mag)
Fig. 2. Precision in measuring the sizes of asteroids with Gaia depends mainly on
photons noise statistics. Precision depends on magnitude and angular size. The apparent
magnitude-angular size plane can be divided in two regions by the solid line representing
the cases of measurements with a precision of 10%. The upper region corresponds to cases
of measurements with a precision better than 10%, while the lower one corresponds to
the measurements with a precision worse than 10%.
