Vikram Sarabhai Space Centre (VSSC) in
Thiruvananthapuram launches a Rohini sounding rocket on Friday with equipments
to investigate the effects of the annular solar eclipse on the atmosphere.
15 January 2010
The Vikram Sarabhai Space Centre (VSSC) launched a
total of 11 Rohini series indigenous sounding rockets from the Thumba
Equatorial Rocket Launching Station here and the Satish Dhawan Space Centre in
Sriharikotta to investigate the effects of the longest annular solar eclipse of
this millennium, which occurred on Friday, on the earth’s atmosphere.
On Thursday, the VSSC launched two sounding rockets
each of type RH 300 Mk II and RH 200, and on Friday, three sounding rockets of
type RH 300 Mk II and two sounding rockets of RH 200 from Thumba. The RH 300 Mk
II rockets can shoot to a peak altitude of 116 km above the earth and the RH
200 a peak altitude of 70 km above the earth.
Two larger Rohini rockets of the series RH 560 Mk II
series were also launched by the VSSC from Sriharikotta, one each on Thursday
and Friday. These rockets are capable of shooting up to a peak altitude of 548
km.
The eclipse assumed annular condition at 1.14 pm over
Thumba. The maximum obscuration of 91 per cent of the sun occurred at 11.15 pm.
The annular phase of the eclipse lasted about 11 minutes and eight seconds over
Thumba. The firing of the sounding rockets were scheduled in such a way as to
collect relevant data on atmospheric structure and dynamics at different
altitudes from the earth before, during and after the annular solar eclipse.
“Many scientifically interesting phenomena occur in the
diurnal equatorial atmosphere [during an eclipse]. Equatorial electrojet,
equatorial ionization anomaly and equatorial temperature and wind anomaly are
examples of such phenomena. When 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.
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 VSSC said.
The results of these experiments would be correlated
with ground-based eclipse observations. The interpretation of the eclipse data
together with the space data is expected to give new insights into earlier
eclipse observations also, the VSSC said.
Spectacular
sight
TSS Subramanian reports from Chennai:
“Man is curious to understand nature,” declared an
Indian Space Research Organisation (ISRO) scientist as the spectacular sight of
the annular solar eclipse appeared in the sky and five sounding rockets sped
into the atmosphere in a span of four hours from the beachfront at Thumba in
Thiruvananthapuram on Friday afternoon.
An ISRO scientist said from Thumba: “It was a
spectacular sight. It was an exhilarating experience. On the one hand, there
was the awe-inspiring sight of the moon covering the disc of the afternoon sun,
which could be safely seen only through a filter. On the other hand, there was
the roar of five sounding rockets zooming into the sky one after another,
complete with a countdown and commentary.”
Impact on
electrojet
The scientist explained that when the eclipse occurred,
the solar radiation was suddenly cut off. This impacted on the electrojet—an
intense band of current system at an altitude of about 100 km and the structure
and the dynamics of the upper atmosphere. The dynamics, that is, the various
processes such as turbulence and eddies occurring in the atmosphere, had a
bearing on the transmission of the global positioning system’s (GPS) signals.
“Hence the study of such rare phenomenon such as the
annular solar eclipse is not only intellectually rewarding but has useful,
long-term practical applications,” he added.
MYS Prasad, Associate Director, SDSC, said the RH-560
lifted off at 1.15 p.m. and reached an altitude of 523 km. “Everything went as
per predictions. The rocket performance was good. The payload data will be
collected and given to scientists,” Dr. Prasad said.
Eclipse at
http://beta.thehindu.com/news/national/article80825.ece