GSLV Mk II rocket transporter. Credit: ISRO

The Indian Space Research Organization’s (ISRO’s) annual report for 2019-2020 lists a bunch of future space missions that India’s premier, albeit only, space organization plans to undertake. Among other things, there are some unique space science missions that ISRO aims to launch within the next five years.

Specialized X-ray telescope

India’s first space telescope, Astrosat, was designed to observe high-energy cosmic objects in multiple wavelengths. The country’s second space telescope, X-ray Polarimetry Satellite (XPoSat), will be smaller and specialized. Launching on a PSLV rocket in 2021, XPoSat will study the polarization of X-rays emitted by cosmic objects from Earth orbit. How radiation is polarized gives away the nature of its source, including the strength and distribution of its magnetic fields and radiation around it.

To this day, the Crab Nebula remains the only X-ray source for which scientists have measured the polarization. XPoSat is expected to provide the same information about the 50 brightest known sources in the universe, including pulsars, X-ray binary stars and gigantic-black-hole-hosting galactic cores.

XPoSat and its polarimeter instrument POLIX. Credit: ISRO

XPoSat’s polarimeter instrument works in the medium X-ray region, specifically 8–30 keV. It is being built and tested by scientists at the Raman Research Institute.

Collaboration with NASA on a radar-imaging satellite

The NASA-ISRO Synthetic Aperture Radar (NISAR) satellite will be the first satellite with a dual-frequency radar imaging system. At $1.5 billion, it’s among the most expensive Earth-observation satellites ever built. Following its planned launch onboard a GSLV Mk II rocket in 2021, it will be placed in a Sun-synchronous orbit so that its solar panels can provide constant power.

An artist’s impression of the NASA-ISRO Synthetic Aperture Radar. Credit: NASA

NISAR’s dual-frequency radar imaging system will reveal ongoing changes in Earth’s crust, polar ice, climatic processes, biomass, etc., at a high resolution of 3–50 m, at a rapid bi-weekly pace, globally. The satellite will also be used for disaster management, whereby its data will be available only a few hours after observations. ISRO and NASA have said they’ll place all science data from the mission in the public domain.

India’s first solar observatory

Launching in late 2021/early 2022 onboard a PSLV-XL rocket, Aditya-L1, it will be placed at the first Lagrangian point (L1) between the Sun and Earth, where the dynamic gravitational attraction between these two bodies roughly cancel out. From there, it will observe the Sun’s surface and atmosphere with its seven instruments.

A schematic illustration of Aditya-L1 and its instruments. Credit: ISRO

The L1 point is not a point as much as a small region in space, host to multiple solar science missions in the past, such as SOHO, ACE, WIND, DSCOVR, etc. Like those, Aditya-L1 will observe the Sun uninterrupted from this vantage point. The spacecraft’s uniqueness is the ability to observe the Sun in multiple wavelengths while also measuring the solar magnetic field and the solar wind radiation using its in-situ instruments.

In 2018, NASA launched the Parker Solar Probe on a mission to go right into the Sun’s atmosphere to unravel its mysteries! ESA also launched the Solar Orbiter this year on a similar mission except it’ll study the Sun from a bit farther away but still closer in than Mercury. Aditya-L1 will study the Sun from much further away but its global views will allow for its observations to complement data from the NASA and ESA probes.

The hope for scientists globally with these solar missions is to explain why the Sun’s corona is hotter than its surface by several million degrees. This is a major unsolved problem in solar physics.

A Venus orbiter in the making

Last year, ISRO called for instrument proposals for a Venus orbiter mission, Shukrayaan, to be launched in 2023. This is great because an initial interest in exploring the planet, in the 1960s and 1970s, quickly faded after Mars started getting all the attention.

A not-to-scale representation of ISRO’s Venus orbiter mission Shukrayaan.

Venus needs to be explored not just because it hosted water for at least 2 billion years, longer than Mars, but also to understand how Earth-like planets change over time, and what makes Earth a haven for life. Right now, there is only one spacecraft at Venus, the Japanese orbiter Akatsuki, compared to eight at Mars and three more on its way. So ISRO sending a mission to Venus should be refreshing for the global planetary science community.

Shukrayaan is expected to have a payload capacity of 100 kg and the spacecraft will be placed in a highly elliptical orbit of 500 ✕ 60,000 km, allowing for both closeup and global observations. In addition to the room for 12 Indian instruments, ISRO will also be adding a few international ones. This is great, as attested by Chandrayaan 1’s co-discovery of water on the Moon with NASA.

The primary scientific objectives of Shukrayaan include studies of Venus’ surface and subsurface, its atmospheric chemistry and solar wind interactions with the planet. NASA has expressed interest in sending a terahertz instrument onboard the orbiter to see through Venus’s thick atmosphere and observe chemical reactions below.

Other missions in ISRO’s pipeline include a follow-up of the Mars Orbiter Mission in 2024. It’ll likely be an orbiter similar to Shukrayaan in terms of payload capacity. There are also plans to follow up on Astrosat and Chandrayaan 2 but details are unclear at the moment.

Given ISRO’s fairly nascent space science program, the boost to such missions is a welcome trajectory for India’s space exploration endeavors. Here’s hoping that India goes all in on this trend and makes deep space exploration a prioritized national goal just like it has done to launch astronauts.