ISRO eyes June-July launch for solar mission, receives primary payload

The Indian Space Research Organisation (Isro) is targeting a June-July time frame to launch Aditya L1, India’s first dedicated scientific mission to study the Sun, Isro Chairman and Secretary, Department of Space, S Somanath said on Thursday. He was speaking at an event in Hosakote that marked the formal handing over of Visible Line Emission Coronagraph (VELC), the mission’s primary payload developed by the Indian Institute of Astrophysics (IIA).

“Currently, we are getting the (Aditya L1) satellite ready. The payload will reach the U R Rao Satellite Centre and will be integrated with the satellite. It will go through extensive testing and evaluation and will be launched on the PSLV, by June-July,” Somanath said.

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The satellite with seven payloads will be launched to the L1 orbit – the first Lagrangian point of the Sun-Earth system, about 1.5 million km from the Earth – from where it can view the sun continuously, without blockage.

The primary payload

The 90-kg VELC was assembled, tested, and calibrated at the IIA’s Centre for Research and Education in Science and Technology campus in Hosakote. The payload took about 15 years in the making, from concept to realisation.

VELC is designed to facilitate continuous observations of the Sun’s atmosphere, the Corona. The extremely bright light from the Sun’s surface, or disk, makes observation of the lower Corona very difficult. VELC comes with an ‘internal occulter’ that separates out this light, discards it, and sends the remaining light (from the Corona) for processing.

“It can image the solar Corona as close as 1.05 times the solar radius. It can also do imaging, spectroscopy, and polarimetry at the same time, and can take observations at a very high resolution and many times a second,” Prof B Raghavendra Prasad, Principal Investigator of VELC, said.

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Uninterrupted observations of the Corona are critical in studying the gap between temperatures in the Sun’s atmosphere (about a million degrees) and its surface (only about 6,000 Kelvin), IIA said.

VELC is designed to study processes that lead up to the heating of the Corona and solar wind acceleration, aspects of space weather, and measurement of coronal magnetic fields.

There are six other payloads on Aditya L1, developed by Isro and other institutions-

1. Solar Ultraviolet Imaging Telescope (SUIT) – to provide full disk images of the solar atmosphere

2. Solar Low Energy X-Ray Spectrometer (SoLEXS) – to study the coronal heating mechanism

3. High Energy L1 Orbiting X-Ray Spectrometer (HEL1OS) – to observe dynamic/eruptive events in the Corona

4. Aditya Solar Wind Particle Experiment (ASPEX) – to study solar wind and its spectral characteristics

5. Plasma Analyser Package for Aditya (PAPA) – to understand the composition of solar wind plasma and its energy distribution

6. Magnetometer – to measure the magnitude and nature of the interplanetary magnetic field.