SARAL (''S''atellite with ''AR''gos and ''AL''tiKa) 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. The m ...

technology mission of

Indian Space Research Organisation The Indian Space Research Organisation (ISRO; ) is the national space agency of India, headquartered in Bengaluru. It operates under the Department of Space (DOS) which is directly overseen by the Prime Minister of India, while the Chairman o ...

(ISRO) and Centre National d'Études Spatiales (

CNES The (CNES; French: ''Centre national d'études spatiales'') is the French government space agency (administratively, a "public administration with industrial and commercial purpose"). Its headquarters are located in central Paris and it is und ...

). SARAL performs altimetric measurements designed to study

ocean circulation An ocean current is a continuous, directed movement of sea water 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.

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 mission of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

NOAA The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...

and CNES / EUMETSAT. It will fill the gap between

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

and the Sentinel-3 mission of the European

Copernicus Programme Copernicus is the European Union's Earth observation programme coordinated and managed for the European Commission by the European Union Agency for the Space Programme in partnership with the European Space Agency (ESA), the EU Member States. ...

(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 ex ...

(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 opposed to specially produced satellites. Bus- ...

( 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) satellites ...

), 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 Franco-Italian aerospace manufacturer. A joint venture between the French technology corporation Thales Group (67%) and Italian defense conglomerate Leonardo (33%), the company is the largest satellite manufactur ...

(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 space system used by operators and support personnel, as opposed to the space segment and user segment. The ground segment enables management of a spacecraft, and distribution of pay ...

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. It was built by the French National Space Agency,

. 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), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

. 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 the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...

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.

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 (CanX-3a), both of

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

. 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, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sa ...

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

NEOSSat 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 arcseconds ...

(

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 ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...

with a mass of ~74 kg. •

AAUSAT3 AAUSat-3, (Aalborg University CubeSat-3), is the third CubeSat built and operated by students from the Aalborg University in Denmark. It was launched on 25 February 2013 from the Satish Dhawan Space Centre in India on a Polar Satellite Launch ...

(Aalborg University CubeSat-3), a student-developed nanosatellite (1U CubeSat) of AAU,

Aalborg Aalborg (, , ) is Denmark's List of cities in Denmark by population, fourth largest town (behind Copenhagen, Aarhus, and Odense) with a population of 119,862 (1 July 2022) in the town proper and an Urban area, urban population of 143,598 (1 July ...

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of Denmark , establish ...

. 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, around southwest 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 name "Guildf ...

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and ...

. 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 research university in Toronto, Ontario, Canada, located on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution ...

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.

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)