Solar Submillimeter-wave Telescope

   SST 212 GHz and 405 GHz Observations at El Leoncito

1. SST observes the Sun with a cluster of 6 beams, shown in the diagram, 4 at 212 GHz with approximate HPBW of 4', and 2 at 405 GHz with approximate HPBW of 2' (Kaufmann et al., 2001; 2008). Tracking of source on the Sun is positioned on beam 5.
2. Data are presented in units of antenna temperatures, corrected for atmospheric transmission. Adimensional scintillation indices are shown, as described below.
3. The reliability of submm-wave observations is critically dependent on atmospheric transmission. Opacity τ in nepers is determined several times each day, by fitting the atmosphere temperature dependence on elevation angle (the "tipping" tecnique). This works at 212 GHz, but not well at 405 GHz, for τ > 2.2 nepers. The attenuation is better calculated from the relationship τ(405) = 0.09 + 4.43 τ(212) determined from extinction and solar brightness measurements method (Melo et al., 2005).

4. For bursts click on the "On Source-Multiple beams" mode to calculate the excess corrected antenna temperature at 212 and 405 GHz at the position the source is in relation to the beam positions, deduced from the comparison of partially overlapping 212 GHz beams 2, 3 and 4 using the multiple beam technique (Georges et al., 1989; Gimenez de Castro et al., 1999).
   Attention: For selected time structures that do not correspond to actual bursts the calculations may produce inconsistent results.
   
5. The baselines previous to the event above which the burst excess temperatures ΔT are set at the time of the initial time scale. The antenna temperature corrected for the source position in relation to the beams are converted into solar flux units S = 0.62 ΔT (at 405 GHz) and S = 0.35 ΔT (at 212 GHz), assuming aperture efficiencies of about 0.2 and 0.35, respectively. Uncertainties of the order of ± 20% arise from approximations made on atmospheric transmission, gains and on the irregular beams shapes in space.
6. Scintillation indices are defined as the ratio of the 40 ms data sigma of fluctuations over the solar mean value above the sky level, taken every 3 seconds. They are useful for quick detection of pulsations of distinct nature: solar origin, atmospheric opacity variations or instrumental.

References

Georges, C. B. et al., Proc. of SBMO-International Microwave and Optoelectronic Conference/IEEE-MTT (cat. Nr. N89th0260-0), Rio de Janeiro, Brazil, p. 447, 1989.
Giménez de Castro, C. G. et al., Astron. Astrophys., 140, 343, 1999.
Kaufmann, P. et al., Proc. of 2001 SBMO-International Microwave and Optoelectronic Conference/IEEE-MTT (cat. Nr. 01TH8568), p. 439, Belem, Brazil, 2001.
Kaufmann, P. et al., Proc. of SPIE, 7012, 7012L1.2008.
Melo, A. M. et al., IEEE Trans. Ant. Propagat., 53, 1528, 2005.

Presentations (click one of the options)

1) SST Calibrated Data (click here)

Updated every hour.

• SST beams positions on the solar disk and atmospheric attenuation.
• Corrected antenna temperatures, all channels, 40 ms data points, smoothed along one second.
• Scintillation index, all channels.

ZOOM mode is obtained clicking at two successive times to obtain the corresponding time-expanded plot. ZOOM plots options:

• Corrected antenna temperatures, all channels, 40 ms data points.
• Scintillation index, all channels.
• On Source - Multiple beams.

2) Qualitative real time on-line monitoring

Exhibits plots of channels 2 (212 GHz) and 5 (405 GHz) in relative units (above) and scintillation index (below).