Venus Orbiter Mission

The Venus Orbiter Mission, unofficially known as Shukrayaan     (Sanskrit:  'Venus',  'Craft, Vehicle'), is a planned Indian Space Research Organisation (ISRO) mission to study the surface and atmosphere of Venus.

Funds were released in 2017 to complete preliminary studies, and solicitations for instruments were announced. The orbiter was expected to have a science payload capability of approximately 100 kg with 500 W available power. The initial elliptical orbit around Venus is expected to be 500 km at periapsis & 60000 km at apoapsis.

Objectives
The three broad research areas of interest for this mission include surface/subsurface stratigraphy and re-surfacing processes; studying the atmospheric chemistry, dynamics and compositional variations, and studying solar irradiance and solar wind interaction with Venus' ionosphere. The mission may carry out research on Venus' active volcanic hotspots, lava flows and their patterns. The probe may reexamine claims of phosphine on Venus, as the findings are currently thought to be in error.

Status
Based on the success of Chandrayaan and the Mars Orbiter Mission, ISRO began studying the feasibility of interplanetary missions to Mars and Venus. A mission to Venus was first presented at a Tirupati space meet in 2012. ISRO was authorized to complete preliminary studies. From 2016 to 2017, ISRO collaborated with Japan Aerospace Exploration Agency (JAXA) to study the Venus atmosphere using signals from the Akatsuki in a radio occultation experiment.

In 2017, ISRO made an 'Announcement of Opportunity' (AO) seeking science payload proposals from Indian academia. In 2018, ISRO made another 'Announcement of Opportunity' inviting payload proposals from the international scientific community. The available science payload capacity with a science payload of 100 kg.

ISRO and the French National Centre for Space Studies (CNES) held collaboration discussions in 2018, including the Venus mission and autonomous navigation and aerobraking technologies. French astrophysicist Jacques Blamont expressed interest to ISRO chairman Udupi Ramachandra Rao to use balloons to help study the Venusian atmosphere. Similar to the Vega missions, these instrumented balloons could be deployed from an orbiter and take prolonged observations while floating in the planet's relatively mild upper atmosphere. ISRO agreed to consider the proposal to use a balloon probe carrying a 10 kg payload to study the Venusian atmosphere at a 55 km altitude.

As of late 2018, the Venus mission was in the configuration study phase and ISRO had not sought the Indian government's full approval. Somak Raychaudhury, the director of Inter-University Centre for Astronomy and Astrophysics (IUCAA), stated in 2019 that a drone-like probe was being considered.

As of November 2020, ISRO had shortlisted 20 international proposals that include collaboration with institutions from Russia, France, Sweden and Germany. Mission could be launched no earlier than 2028, with an alternate launch window in 2031.

S. Somanath, the chairman of ISRO, stated that engineers are aiming to lower the cost of some high-value components and that India's maiden mission to Venus is probably going to launch in 2028 while speaking with reporters during India International Science Festival 2024. Venus Orbiter Mission development, however, will take longer than expected because Gaganyaan project has taken precedence.

Science payload
The 100 kg science payload would consist of instruments from India and other countries. , 16 Indian and 7 international payloads had been shortlisted.

Indian instruments

 * Venus L & S-Band SAR
 * VARTISS (Orbital Ground-penetrating radar)
 * VSEAM (Surface Emissivity)
 * VTC (Thermal Camera)
 * VCMC (Cloud Monitoring)
 * LIVE (Lightning Sensor)
 * VASP (Spectro Polarimeter)
 * SPAV (Solar occultation photometry)
 * NAVA (Airglow imager)
 * RAVI (RO Experiment)*
 * ETA (Electron Temperature Analyser)
 * RPA (Retarding Potential Analyser)
 * Mass Spectrometer
 * VISWAS (Plasma Analyser)*
 * Venus Radiation environment monitor (VeRad)
 * Venus Solar Soft x-ray Spectrometer (VS3)
 * VIPER (Plasma Wave Detector)
 * VODEX (Dust experiment)
 * * RAVI and VISWAS are being proposed as collaborations with Germany and Sweden.

International instruments
Two Russian payloads by the Russian Space Research Institute and Moscow Institute of Physics and Technology were shortlisted to study the atmosphere:
 * Terahertz devices to generate powerful radar pulses. Proposed by NASA.


 * VIRAL (Venus InfraRed Atmospheric Gases Linker) by Space Research Institute, Moscow (after their collaboration with LATMOS, France ended).
 * IVOLGA: A laser heterodyne NIR spectrometer for studying the structure and dynamics of the Venusian mesosphere.