VSSC launches 11 sounding rockets to study annular solar eclipse

The Vikram Sarabhai Space Centre (VSSC) at Thiruvananthapuram today launched as many as 11 Rohini series of indigenous sounding rockets to investigate the effects of the annular solar eclipse on the atmosphere.

The longest annular eclipse of this millennium occurred today and was visible best from the southern tip of the country.

The Indian Space Research Organisation (ISRO) said the rockets were launched from the Thumba Equatorial Rocket Launching Station (TERLS) at Thumba in Thiruvananthapuram district and the Satish Dhawan Space Centre (SDSC), Sriharikota.

All the payloads (scientific instruments) of the rockets were developed in-house by VSSC, an ISRO press release said.

According to it, yesterday, two Rohini sounding rockets of the type RH 300 Mk II were launched at 12:20 pm and 1:05 pm respectively. This was followed by two RH 200 launches at 1:07 pm and 3 pm.

Following the same pattern, another four launches were carried out today. Later, one more sounding rocket of RH 300 Mk II type was launched at 4 pm today. Two larger Rohini rockets of the series RH 560 MK II were also launched from SDSC, one each yesterday and today, which had a peak altitude of 548 km.

Today at around IST 1:14 pm, the eclipse passed close to TERLS with 91% obscuration. The obscuration of Sun during the eclipse was about 11 min 08 sec. The maximum obscuration occurred around 1:15 pm. All the sounding rocket launches were conducted to study the effects of the annular solar eclipse on the atmospheric structure and dynamics, the release said.

The release said many scientifically interesting phenomena occur in the diurnal equatorial atmosphere. Equatorial Electrojet (EEJ), Equatorial Ionization Anomaly (EIA) and Equatorial Temperature and Wind Anomaly (ETWA) are examples of such phenomena.

When a solar eclipse occurs, there will be a sudden cut-off of solar radiation. This cut-off will affect the atmospheric structure and dynamics and there will be a large reduction in ionization and temperature.

The release said today's eclipse offered a unique opportunity to scientists to investigate the effects of fast varying solar flux on the photochemistry and electrodynamics of the different atmospheric regions, especially the equatorial mesopause and ionosphere-thermosphere regions.

The main payload instruments that flew in the sounding rockets during these experiments are:

  • Langmuir Probes and Electric Field Probes to study the characteristics of E-region plasma waves and generation process associated with sub-meter waves in relation to plasma temperature.

  • Trimethyl Aluminum Experiment (TMA) to derive neutral winds using TMA trails, ground based photography and a chain of magnetometers.

  • Electron density and Neutral Wind (ENWi) Probe consisting of a velocity probe and a Langmuir probe, for measurement of ionospheric E-region neutral winds, electron density and irregularity strength.

  • Earth's Atmospheric Composition Explorer (EACE) - to make very fast measurements on the neutral atmospheric composition. The measurements were taken in a scanning mode during the ascent and descent of the rocket flights during and after the eclipse.

  • Chaff Experiment to investigate the temperature and horizontal wind perturbations in the middle atmosphere.

The release said the results of these experiments will coordinate ground-based eclipse observations with in situ space measurements. Interpretation of eclipse data together with space data is expected to give new insights to the earlier eclipse observations.

This was the first ISRO effort to realise sounding rocket systems for a record 11 flights during a short period of two days from TERLS and SDSC, the release added.

[caption id="attachment_121" align="aligncenter" width="175" caption="Vikram Sarabhai Space Centre Conducts a Series of Sounding Rocket Launches to Study the Annular Solar Eclipse on January 14, 2010."][/caption]

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