Indian Data Relay Satellite System or IDRSS is a planned Indian

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Inter-satellite communications satellites. It is planned to initially comprise two satellites, CMS-04 (formerly IDRSS-1) & IDRSS-2 in

geostationary orbit A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...

. It will facilitate relay of information between various Indian spacecraft, in-flight launch vehicle monitoring and assist Indian Human Spaceflight Programme.

Objectives

A Data Relay Satellite System (DRSS) facilitates continuous real-time communication between

Low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

bound spacecraft to the

ground station A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves fro ...

as well as inter-satellite communication. Such a satellite in geostationary orbit can track a low altitude spacecraft up to almost half of its orbit.

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

operates one of world's largest

remote sensing Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth ...

satellites systems. Visibility of these satellites is not more than 10-15 minutes in a day and sometimes even lower. The IDRSS satellites, one opposite to each half of earth in

GEO Geo- is a prefix derived from the Greek word ''γη'' or ''γαια'', meaning "earth", usually in the sense of "ground or land”. GEO or Geo may also refer to: Arts, entertainment, and media * ''GEO'' (magazine), a popular scientific magazine ...

, can see about 80 per cent of the area where Indian remote sensing satellites are orbiting, hence enhancing visibility range and data transfer rates of satellites. IDRSS can also monitor a launch vehicle from the time it lifts off from the launch pad. Satellites will hereby also reduce dependency on ground stations. Implementation of the system will be essential for tracking

Gaganyaan Gaganyaan (Sanskrit IAST: ''gagan-yāna'', ) is an Indian crewed orbital spacecraft intended to be the formative spacecraft of the Indian Human Spaceflight Programme. The spacecraft is being designed to carry three people, and a planned upgrad ...

's future crewed spacecraft. The main objectives of IDRSS are: * TTC, Data, Audio and Video links to Gaganyaan * TTC links to LEO satellite * Data transfer from Antarctica Ground Stations

Design

IDRSS satellites would be based on 2,000 kg class, I-2K extended bus and will be compatible for launch onboard GSLV Mk-II Launch Vehicle.

Payload

* Data relay payloads operating in S, Ka and Ku bands. * 2.5 m deployable Cassegrain antenna System operating in dual frequency bands (S and Ka bands) * 1.5 m fixed Cassegrain Antenna System operating in Ku and Ka frequency bands. The deployable antenna system will interface with the satellite by means of a deployable, pointing and tracking mechanism along with a S band rotary joint. Satellites might carry

optical communication Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date b ...

payload for increased data security and high transfer rates.

Satellites

Launch

IDRSS was approved by

Government of India The Government of India (ISO: ; often abbreviated as GoI), known as the Union Government or Central Government but often simply as the Centre, is the national government of the Republic of India, a federal democracy located in South Asia, c ...

and had funds allocated in budget of 2019-20. CMS-04 would be the first spacecraft in the IDRSS constellation, and its launch is currently scheduled for 2023.

References