SARAL (Satellite with ARgos and ALtiKa) is a cooperative

altimetry An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. T ...

technology mission of

Indian Space Research Organisation The Indian Space Research Organisation (ISRO ) is India's national List of government space agencies, space agency, headquartered in Bengaluru, Karnataka. It serves as the principal research and development arm of the Department of Space (DoS), ...

(ISRO) and

Centre National d'Études Spatiales CNES () is the French national space agency. Headquartered in central Paris, the agency is overseen by the ministries of the Armed Forces, Economy and Finance and Higher Education, Research and Innovation. It operates from the Toulouse Spac ...

(CNES). SARAL performs altimetric measurements designed to study

ocean circulation An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, ...

and

sea surface elevation Ocean surface topography or sea surface topography, also called ocean dynamic topography, are highs and lows on the ocean surface, similar to the hills and valleys of Earth's land surface depicted on a topographic map. These variations are exp ...

Mission

A CNES / ISRO MOU ( Memorandum of Understanding) on the SARAL mission was signed on 23 February 2007. The SARAL mission is complementary to the

Jason-2 OSTM/Jason-2, or Ocean Surface Topography Mission/Jason-2 satellite, was an international Earth observation satellite altimeter joint mission for sea surface height measurements between NASA and CNES. It was the third satellite in a series ...

mission of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

NOAA The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...

and CNES /

EUMETSAT The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) is an intergovernmental organisation created through an international convention agreed by a current total of 30 European Member States. EUMETSAT's primary ...

. It will fill the gap between

Envisat Envisat ("Environmental Satellite") is a large Earth-observing satellite which has been inactive since 2012. It is still in orbit and considered space debris. Operated by the European Space Agency (ESA), it was the world's largest civilian Ear ...

and the Sentinel-3 mission of the European

Copernicus Programme Copernicus is the Earth observation component of the European Union Space Programme, managed by the European Commission and implemented in partnership with the Member state of the European Union, EU member states, the European Space Agency (ES ...

(Global Monitoring for Environment and Security - GMES programme). The combination of two altimetry missions in orbit has a considerable impact on the reconstruction of

sea surface height Ocean surface topography or sea surface topography, also called ocean dynamic topography, are highs and lows on the ocean surface, similar to the hills and valleys of Earth's land surface depicted on a topographic map. These variations are exp ...

(SSH), reducing the mean mapping error by a factor of 4.

Instruments

The SARAL payload module was provided by CNES: ALtiKa (Ka-band altimeter), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), Laser Retroreflector Array (LRA), and ARGOS data collection system. ISRO is responsible for the

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are less customized than specially-produced satelli ...

( Indian Mini Satellite-2), launch (

Polar Satellite Launch Vehicle The Polar Satellite Launch Vehicle (PSLV) is an expendable medium-lift launch vehicle designed and operated by the Indian Space Research Organisation (ISRO). It was developed to allow India to launch its Indian Remote Sensing (IRS) satellite ...

), and operations of the satellite.

ARGOS Advanced-Data Collection System (A-DCS)

Argos-3 of French National Space Agency (CNES), manufactured by

Thales Alenia Space Thales Alenia Space () is a joint venture between the French technology corporation Thales Group (67%) and Italian defense conglomerate Leonardo (company), Leonardo (33%). The company is headquartered in Cannes, France. It provides space-based ...

(TAS). ARGOS contributes to the development and operational implementation of the global ARGOS Advanced-Data Collection System. It will collect a variety of data from ocean buoys to transmit the same to the ARGOS

ground segment A ground segment consists of all the ground-based elements of a spaceflight, space system used by operators and support personnel, as opposed to the Satellite space segment, space segment and user segment. The ground segment enables management of ...

for subsequent processing and distribution.

Ka-band altimeter (ALtiKa)

ALtiKa, the altimeter and prime payload of the SARAL mission, is the first spaceborne altimeter to operate at

Ka-band The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum. The designation "Ka-band" is from Kurz-above, which stems from the German word ''kurz,'' meaning "short". There ...

. It was built by the French National Space Agency,

CNES CNES () is the French national space agency. Headquartered in central Paris, the agency is overseen by the ministries of the Armed Forces, Economy and Finance and Higher Education, Research and Innovation. It operates from the Toulouse Spac ...

. The payload is intended for oceanographic applications, operates at 35.75

GHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...

. ALTIKA is set to take over ocean-monitoring from

. It is the first to operate at such a high frequency, making it more compact and delivering better performance than the previous generation. While existing satellite-borne altimeters determine sea level by bouncing a radar signal off the surface and measuring the return-trip time, ALtiKa operates at a high frequency in Ka-band. The advantage of this is twofold. One, the

atmosphere of Earth The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather ...

slows down the radar signal, so altimetry measurements are skewed and have to carry additional equipment to correct for this error. Since ALTIKA uses a different system, it does not have to carry an instrument to correct for atmospheric effects as current-generation altimeters do. ALtiKa gets around this problem by operating at a high frequency in Ka-band. Another advantage of operating at higher frequencies is greater accuracy. ALtiKa will measure ocean surface topography with an accuracy of 8 mm, against 2.5 cm on average using current-generation altimeters, and with a spatial resolution of 2 km. The disadvantage, however, is that high-frequency waves are extremely sensitive to rain, even drizzle. 10% of the data is expected to be lost. (Although this could be exploited to perform crude measurements of precipitation).

DORIS

DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite): DORIS is a dual-frequency tracking system (400 MHz and 2 GHz) based on network of emitting ground beacons spread all over the world.

Laser Retroreflector Array (LRA)

LRA is provided by CNES. The objective of LRA is to calibrate the precise orbit determination system and the altimeter system several times throughout the mission. The LRA is a passive system used to locate the satellite with laser shots from ground stations with an accuracy of a few millimeters. The reflective function is done by a set of 9 corner cube reflectors, with a conical arrangement providing a 150º wide field of view over the full 360°

azimuth angle An azimuth (; from ) is the horizontal angle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system. Mathematically, the relative position vector from an observer ( origin) to a point of in ...

Applications

SARAL data products is useful for operational as well as research user communities in many fields like: * Marine meteorology and sea state forecasting * Operational oceanography * Seasonal forecasting * Climate monitoring * Ocean, Earth system and climate research * Continental ice studies * Protection of biodiversity * Management and protection of marine ecosystem * Environmental monitoring * Improvement of maritime security

Secondary payloads

The six secondary payloads manifested on this flight were: • BRITE-Austria (CanX-3b) and

UniBRITE UniBRITE-1 is, along with TUGSAT-1, one of the first two Austrian satellites to be launched. Along with TUGSAT, it operates as part of the BRIght Target Explorer constellation of satellites. The two spacecraft were launched aboard the same rocke ...

(CanX-3a), both of

Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...

. UniBRITE and BRITE-Austria are part of the BRITE Constellation, short for "BRIght-star Target Explorer Constellation", a group of 6.5 kg, 20 cm x 20 cm x 20 cm nanosatellites who purpose is to photometrically measure low-level oscillations and temperature variations in the sky's 286 stars brighter than visual magnitude 3.5. •

Sapphire Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name ''sapphire ...

(Space Surveillance Mission of Canada), a minisatellite with a mass of 148 kg. • NEOSSat (

Near Earth Object Surveillance Satellite The Near Earth Object Surveillance Satellite (NEOSSat) is a Canadian microsatellite using a 15-cm aperture f/5.88 Maksutov telescope (similar to that on the MOST spacecraft), with 3-axis stabilisation giving a pointing stability of ~2 arcsecon ...

), a microsatellite of

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

with a mass of ~74 kg. • AAUSAT3 (Aalborg University CubeSat-3), a student-developed nanosatellite (1U CubeSat) of AAU,

Aalborg Aalborg or Ålborg ( , , ) is Denmark's List of cities and towns in Denmark, fourth largest urban settlement (behind Copenhagen, Aarhus, and Odense) with a population of 119,862 (1 July 2022) in the town proper and an Urban area, urban populati ...

Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...

. The project is sponsored by DaMSA (Danish Maritime Safety Organization). •

STRaND-1 STRaND-1 (Surrey Training, Research and Nanosatellite Demonstrator 1) is a failed 3U CubeSat developed by Surrey University's Surrey Space Centre (SSC) and Surrey Satellite Technology (SSTL). The nanosatellite was launched into orbit on board a ...

(Surrey Training, Research and Nanosatellite Demonstrator), a 3U CubeSat (nanosatellite) of SSTL ( Surrey Satellite Technology Limited) and the USSC (University of Surrey Space Centre),

Guildford Guildford () is a town in west Surrey, England, around south-west of central London. As of the 2011 census, the town has a population of about 77,000 and is the seat of the wider Borough of Guildford, which had around inhabitants in . The nam ...

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

. STRaND-1 has a mass of ~4.3 kg. The

University of Toronto The University of Toronto (UToronto or U of T) is a public university, public research university whose main campus is located on the grounds that surround Queen's Park (Toronto), Queen's Park in Toronto, Ontario, Canada. It was founded by ...

arranged for the launch to carry three small satellites for universities as part of its Nanosatellite Launch Services program, designated NLS-8: BRITE-Austria, UniBRITE and AAUSat3. The three NLS satellites used the XPOD (Experimental Push Out Deployer) separation mechanism of UTIAS/SFL for deployment. The STRaND-1 nanosatellite was deployed with the ISIPOD CubeSat dispenser of ISIS ( Innovative Solutions In Space).

Launch

SARAL was successfully launched into a

Sun-synchronous orbit A Sun-synchronous orbit (SSO), also called a heliosynchronous orbit, is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. More technically, it is ...

(SSO) on 25 February 2013, at 12:31

UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...

References

External links

Gunter's Space Page - SARAL
{{Indian space programme Spacecraft launched in 2013 Earth observation satellites of India Earth satellite radar altimeters 2013 in India Argos (satellite system)