The scientific objective of the VIRGO experiment (Variability of solar IRradiance and Gravity Oscillations) on board SOHO (Solar and Heliospheric Observatory) is to determine the characteristics of pressure and internal gravity oscillations by observing irradiance and radiance variations, to measure the solar total and spectral irradiance, and to quantify their variability over periods of days to the duration of the mission. With these data helioseismological methods can be used to probe the solar interior. The VIRGO experiment contains two different active-cavity radiometers for monitoring the solar "constant’"(DIARAD and PMO6-V), a low-resolution imager (LOI) with 12 pixels, for the measurement of the radiance distribution over the solar disk at 500 nm, and two three-channel sunphotometers (SPM) for the measurement of the spectral irradiance at 402, 500, and 862 nm.
The performance of the VIRGO instrument Frohlich et al. (1995) was reported by Frohlich et al. (1997). VIRGO is composed of three Sun photometers (5nm bandwidth) operating at 402 nm (blue), 500 nm (green), and 862 nm (red) observing the Sun as a star (the formation height for all three is a few tens of kilometers). VIRGO/SPMs integrate over one minute centered around the full minute. The time series are cleaned of outliers and then detrended with a running mean high-pass filter to remove unwanted low-frequency trends. An additional correction is also applied whenever possible in order to correct for the so-called SPM "attractors" (see Jiménez et al., 2002). The temporal cadence of the available time series is of 60s and the starting date is on April 11, 1996 until March 30, 2014. The duty cycle of the time series is around 96%.
Also use the following in your acknowledgements in publication: "The VIRGO instrument onboard SoHO is a cooperative effort of scientists, engineers, and technicians, to whom we are indebted. SoHO is a project of international collaboration between ESA and NASA."
Maj : 31/01/2017 (3581)