In a historic move, on September 18, 2024, the Union Cabinet of the Government of India has accorded approval for two significant space science missions, viz. the Venus Orbiter Mission (VOM) to study different facets of Venus including its surface and atmosphere, and the Chandrayaan-4 mission, which is meant to collect lunar samples and bring back the same to the Earth. These missions will be major stepping stones to achieve Honb’le Prime Minister’s Space Vision 2047, which envisions India being one of the most impactful space-powers with the Bharatiya Antariksha Station in orbit by year 2035, and Indians having landed on the Moon with indigenous technologies by year 2040. These would necessitate achieving a few technologies like heavy-lift-off launch vehicles, human-rated vehicles, docking technology, high-capacity landers, re-entry technology, to name a few. Technology, along with science, will shape up the country’s space programme roadmap, which has been discussed systematically with the scientists from the national institutes and academia.

Speaking about the scientific aspects, India’s planetary exploration programme is driven by the motivations of comparative planetology to study the similarities and dissimilarities between the planets and natural satellites, and exploring the diversities of the Sun-planet interactions. This programme comprises several space missions to study the Moon, Mars, Venus and other members of the solar system, which will, eventually, bring out the detailed perspective of the solar system. In this context, India has already sent three space missions to Moon in its Chandrayaan series in years 2008, 2019 and 2023 respectively, and one mission to the Mars, as the Mars Orbiter Mission, in year 2014. These missions have created significant scientific impact globally, and materialized several International collaborations in planetary science.

Venus Orbiter Mission (VOM)

The importance of the recently-approved Venus Orbiter Mission lies in the fact that globally it is going to impact the Venusian science. Despite sending several space missions globally, Venus retains its enigma. Early missions in the 1960s and 1970s by NASA and the Soviet Union revealed Venus's scorching surface temperature and dense atmosphere. These missions provided initial insights into the planet's atmospheric composition, surface features, and magnetic environment. Later missions in the 1970s and 1980s, such as Pioneer Venus and Vega, expanded our understanding of Venus's atmosphere, including its composition, circulation, and interaction with the Sun. These missions also collected data on the planet's surface and its geological history. More recent missions, like Venus Express and Akatsuki, have focused on studying the planet's atmospheric dynamics, climate evolution, and surface features. These missions have provided valuable information on the planet's unique characteristics and its potential for habitability in the past.

However, these missions to Venus had limited and narrow spatial coverage either South-polar region or in equatorial belt. Hence it is difficult to build global maps of many phenomena, including winds, waves, and chemical abundances. Venus Orbiter Mission would provide uniform coverage of Venus, thus providing a unique global dataset for future science missions.

The Venus Orbiter Mission will explore the planet's atmosphere, surface, and its interaction with the Sun. Key scientific objectives include examining dust in the Venusian atmosphere, mapping its surface topography in high resolution, studying the solar X-ray spectrum near Venus, analysing Venusian airglow, and investigating sub-surface characteristics. Additionally, the mission will serve as a technology demonstration for ISRO, testing aerobraking and thermal management techniques in the harsh Venusian environment.

For the Venus Orbiter mission (VOM), sixteen Indian payloads, two Indian and international collaborative payloads, and one international payload have been recommended by Experts Review Committee under well-defined broad science themes viz., surface/sub-surface, atmosphere, ionosphere and solar wind Interaction with an aim to explicate the outstanding science questions as well as the gap areas which need further investigations.

The scientific payloads / experiments have been recommended for the Venus Orbiter Mission, as described below:

S-Band Synthetic Aperture Radar for Venus mission (VSAR)
Venus Surface Emissivity and Atmospheric Mapper (VSEAM)
Venus Thermal Camera (VTC)
Venus Cloud Monitoring Camera (VCMC)
Lightning Instrument for VEnus (LIVE)
Venus Atmospheric SpectroPolarimeter (VASP)
Solar occultation photometry for vertical profiling of Aerosols and thin clouds in Venusian atmosphere (SPAV)
Narrow band oxygen Airglow detection in Venusian Atmosphere (NAVA)
VEnus THermosphere Ionosphere composition Analyser (VETHICA)
Venus Advanced Radar for Topside Ionosphere and Subsurface Sounding (VARTISS)
Venusian Electron temperature and Density Analyser (VEDA)
Retarding Potential Analyser (RPA) for the observation of Venusian ionosphere
Venus Ionospheric Plasma wave detectoR (VIPER)
Venus Radiation environment monitor (VeRad)
Solar Soft X-ray Spectrometer (SSXS) for Venus Orbiter
Venus Orbit Dust Experiment (VODEX)
Indian and International Collaborative Payloads: Venus Ionospheric and Solar Wind particle AnalySer (VISWAS) by ISRO & IRI Swedish
Radio Anatomy of Venus Ionosphere (RAVI)
Indian and International Collaborative Payloads: VIRAL (Venus InfraRed Atmospheric gases Linker) by ISRO & IKI, Russia

ISRO