What next for ISRO after Chandrayaan-3 mission?

Context: The Indian Space Research Organisation (ISRO) has a packed schedule after Chandrayaan-3 as it is working on various missions. 

Upcoming missions of ISRO: 

1. ADITYA-L1 Mission: Aditya-L1 is the first Indian space mission to observe the Sun and the solar corona. It would observe:

  i. Sun’s Photosphere
  ii. Chromosphere and
  iii. Corona

• The mission will be launched to the L1 orbit (which is the first Lagrangian point of the Sun-Earth system), which is 1.5 million km from the Earth towards the Sun.
• Aditya-L1 has seven payloads in total, of which the primary payload is the Visible Emission Line Coronagraph (VELC).
  • VELC is designed and fabricated by the Indian Institute of Astrophysics, Bengaluru.
  • It is a solar coronagraph that can image the solar corona as close to the solar disk (It can image it 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, or level of detail, and many times a second.

• Significance:
  • Aditya-L1 would help in understanding the effect of the Sun on the Earth and its surroundings.
  • It would study solar upper atmosphericdynamics (chromosphere and corona) and understand the physics of the solar corona and its heating mechanism.
    • The temperature of the Sun’s corona is extremely high, ranging from 1 to 3 million kelvins (K). This is much hotter than the Sun’s surface, which has a temperature of about 5,500 K.
    • To understand this issue, it will capture near-simultaneous photos of the many layers of the Sun’s atmosphere, revealing how energy is routed and transported from one layer to the next.
  • It would help in understanding the phenomenon of coronal mass ejection, pre-flare and flare activities, dynamics of space weather, propagation of particles and fields etc. This would help in tracking Earth-directed storms and predicting their impact through solar observations. 

2. X-ray Polarimeter Satellite: XpoSat is an ISRO-planned space observatory to study the polarisation of cosmic X-rays. It is India’s first dedicated polarimetry mission to study the dynamics of bright astronomical X-ray sources under extreme conditions. 

• Payloads: The spacecraft will carry two scientific payloads – an X-Ray Polarimeter (POLIX) and X-ray SPECtroscopy and Timing (XSPECT) in a low earth orbit. 

• POLIX will measure the polarimetry parameters (degree and angle of polarization) in the medium X-ray energy range of 8-30 keV photons of astronomical origin. POLIX is expected to observe about 40 bright astronomical sources of different categories during the planned lifetime of the XPoSat mission of about 5 years. 
• XSPECT payload will give spectroscopic information in the energy range of 0.8-15 keV. It would observe several types of sources viz. X-ray pulsars, blackhole binaries, low-magnetic field neutron stars in Low-mass X-ray binaries, Active galactic nuclei and Magnetars. 
• Significance: 
  • By measuring the polarisation of X-rays, astronomers can better understand the geometry and physical processes responsible for X-ray emission in a variety of astrophysical sources to gain insight into their inner dynamics (like emission processes).
    • Astronomical sources, including black holes, neutron stars, active galactic nuclei, and pulsar wind nebulae, present complex emission mechanisms that challenge their current understanding. 
    • By combining polarimetric observations along with spectroscopic and timing measurements, researchers can overcome the limitations of the present understanding of astronomical emission processes. 

3. NISAR: NASA-ISRO Synthetic Aperture Radar is an Earth-observation satellite expected to be launched in January 2024 from Satish Dhawan Space Centre in Andhra Pradesh into a sun-synchronous orbit. 

• The 2,800 kilograms satellite consists of both L-band and S-band synthetic aperture radar (SAR) instruments, which makes it a dual-frequency imaging radar satellite. SAR is capable of penetrating clouds and can collect data day and night regardless of the weather conditions. 

• L-band SAR operates at a frequency of around 1 to 2 GHz. The lower frequency (higher wavelength) of L-band SAR allows it to penetrate through vegetation and soil, making it useful for monitoring changes in forest cover, soil moisture etc.
• S-band SAR operates at a frequency of around 2 to 4 GHz. S-band SAR has a higher resolution than L-band SAR and is typically used for applications where higher detail is required, such as monitoring changes in urban areas or coastal zones. 

• It has a large 39-foot stationary antenna reflector made of a gold-plated wire mesh which will be used to focus the radar signals emitted and received by the upward-facing feed on the instrument structure. The instrument’s imaging swath allows it to image the entire Earth in 12 days.
• Jointly developed by: ISRO and NASA

Significance:

• NISAR satellite with two frequency bands: L-band and S-band will image the seismically active Himalayan region that will create a “deformation map” every 12 days and provide high-resolution all-weather data. 
• Study Earth’s dynamic land and ice surfaces in greater detail and observe subtle changes in Earth’s surfaces. E.g., Track flow rates of glaciers and ice sheets, landslide-prone areas and changes in the coastline etc.
• Spot warning signs of natural disasters, such as volcanic eruptions, earthquakes and landslides. 
• Measure groundwater levels, map agricultural and natural resources and monitor Earth’s forest and agricultural regions to improve understanding of carbon exchange. 

4. INSAT-3DS: ISRO has also lined up the launch of INSAT-3DS, an earth-observation satellite. INSAT–3DS will be placed in the geostationary orbit with coarse resolution and daily multiple imaging capability. It will provide meteorological services to India, as well as search and rescue information and message relays for terrestrial data collection platforms. The satellite will be a follow-up to INSAT-3DR.

5. Test vehicle mission: Before undertaking the Gaganyaan human spaceflight mission, ISRO had planned for two uncrewed missions. The launch of a test vehicle mission, for the validation of the crew escape system for Gaganyaan, the country’s maiden human space flight mission, is planned for the beginning of 2024.