MEXART: I. Sensitivity of the array and observable Inter Planetary ...

Scintillation index
1
0.1
0.01
0.001
15.0 18.1 21.88
26.56
32.46
40.08
Elongation
50.6
Figure 2: Variation of scintillation index with solar elongation angle.
68.02
scintillation index, m, is related to ǫ as m ∝ sin(ǫ) −1.75 (Manoharan et al., 1995) as shown
in figure 2. A lower limit on the scintillation index sets an upper limit on the elongation angle
up to which scintillations can be measured. The lower-limit to the m and the corresponding
upper-limit to the ǫ are given in the table 2, for different detection limits.
6 Scintillation map and observing strategy
The region set by the ǫ limit above are shown in figure 3. For an integration time of 50 ms, the
minimum detectable flux is 0.6 Jy. Assuming that most of the sources are close to the detection
limit, the number of sources that would fall within each zone are given in the table 2. This is
calculated assuming that the lines of sights with elongation angles less than 15 ◦ are not observed
due to strong scattering. Since the telescope is a transit instrument, the above elongation angles
correspond to a transit time (see the table 2). During the transit time the observations can be
carried out. For a source the ON source time is about 5 mins. Assuming 10 mins of observing
time for each source including the OFF source observations, the total data-time is about 31
hours for 5σ and 34 hours for 10σ detection. To acquire the data within the transit time of the
IPS-zone the required receivers are 6 for 5 σ detection and 3 for 10 σ detection. The number
of sources that can be observed with elongation angles less than about 75 degree are about 650.
These sources can be observed using 7 receivers over a transit time of 10 hours.
4