Russian Dnepr conducts record breaking 32 satellite haul

by William Graham

Kosmotras launched a Dnepr rocket from Dombarovsky on Thursday, carrying the United Arab Emirates’ DubaiSat-2, thirty one other satellites – including Peru’s first satellite – and one attached payload. The mission set new records for the most payloads carried into orbit by a single rocket and the smallest satellite ever launched, following lift off at 13:10:16 local time (07:10 UTC).

Dnepr Mission:

The Dnepr launch comes less than thirty hours after an Orbital Sciences Minotaur I rocket placed 29 satellites and two attached payloads into orbit, breaking a record which had previously been held by the Dnepr since 2007.

Although Thursday’s launch carried more payloads than the Minotaur, less of them were to be deployed directly; twenty three satellites were tasked with separating from the Dnepr itself, with the remainder being subsatellites to be deployed from other spacecraft on the mission.

Z21The primary payload for Thursday’s launch was DubaiSat-2 for the Emirates Institution for Advanced Science and Technology, or EIAST.

A 300 kilogram (660 lb) satellite developed by South Korea’s SATREC Initiative, it marks the first flight of the SI-300 satellite bus. DubaiSat-2 is the second remote sensing satellite built for EIAST.

DubaiSat-2 uses SaTReC-i’s SpaceEye-1 configuration, combining the SI-300 bus with a High Resolution Advanced Imaging System or HiRAS multispectral imager. The body of the satellite takes the shape of a hexagonal prism with the cylindrical imager atop it. The spacecraft is 1.50 metres in diameter and, including the imager, 1.95 metres in length.

The HiRAS instrument can produce panchromatic, RGB and near-infrared images with a sampling distance of between 1 and 4 metres (3.3 and 13.1 feet) and swath of at least 12 kilometres (7.5 miles). Data is downlinked using the satellite’s X-band Transmission Unit, consisting of an x-band transponder mounted on a platform allowing it to be rotated along one axis. The x-band downlink provides a datarate of up to 160 megabits per second.

A pair of s-band transmitters and a pair of s-band receivers are used to downlink telemetry and uplink commands to the spacecraft.

DubaiSat-2’s Hall Effect Propulsion System (HEPS) is an ion engine which will be used to help maintain the spacecraft’s orbit. The Japan Aerospace Exploration Agency provided some components, including the Microwave Cathode Unit, as part of an in-orbit testing programme. The cathode is derived from those flown aboard the Hayabusa spacecraft.

Z14South Korea’s Science and Technology Satellite 3 (STSAT-3) was the second of the Dnepr’s major payloads, and was mounted on the lower deck or “Platform B” of the rocket’s payload module. The rest of the payloads except SkySat-1 were installed along with STSAT-3 on the lower deck or Platform B, and will only be deployed once the Platform A satellites, and Platform A itself, have separated.

STSAT-3  was  developed  by  KARI,  SaTReC,  KASI  and  several  university professors. It will be operated by the SaTReC, and carries two instruments; the Multipurpose Infrared Imaging System or MIRIS, and the Compact Imaging Spectrometer (COMIS). A 170-kilogram spacecraft it will operate for at least two years.

STSAT-3 is the fifth STSAT spacecraft to be launched for KARI; STSAT-1 was deployed by a Kosmos-3M rocket in September 2003, and three STSAT-2 satellites were the payloads for the three launches of the Naro-1 rocket developed by KARI in partnership with Khrunichev of Russia. STSAT-2A and 2B failed to orbit, however STSAT-2C was successfully launched earlier this year.

MIRIS, which was developed by the Korea Astronomy and Space Science Institute (KASI), consists of a pair of infrared imagers. The MIRIS Space Observation Camera, MSOC, will be used for a near-infrared astronomy mission to characterise the infrared component of the cosmic background radiation environment.

The MIRIS Earth Observation Camera (MEOC) will be used to produce infrared images of the Earth’s surface. MSOC has an 8 centimetre (3.1 in) aperture, while MEOC’s aperture has a diameter of 10 centimetres (3.9 inches).

COMIS is an imaging spectrometer similar in design to the Compact High Resolution Imaging Spectrometer (CHRIS) instrument on the European Space Agency’s Proba-1 satellite. It will conduct hyperspectral observations in up to 128 bands (18 bands simultaneously)at wavelengths of between 0.4 and 1.05 microns.

It can observe a swath of 26 kilometers at a resolution of 26 metres, or a 30-kilometre swath at a resolution of 60 metres.

STSAT-3 generates power by means of solar panels, producing at least 275 watts of power for the spacecraft.

Z11SkyBox Imaging  is another imaging satellite. An American company, SkyBox intends to use the satellite for commercial Earth imagery. SkySat-1 was developed in-house by a team of Stanford graduates used to working on CubeSats, and its development was based on similar principles with regards minimising costs and unnecessary systems.

The SkySat-1 spacecraft has a mass of 100 kilograms (220 lb), and carries an imaging system which is expected to photograph the Earth at a resolution of up to one metre (3.3 feet). A second satellite will be launched by a Soyuz rocket next year, with the company’s long-term plans calling for a constellation of 24 spacecraft.

AprizeSat-7 and 8 are the ninth and tenth satellites to be launched as part of the AprizeSat constellation, operated by AprizeSat. The constellation, which was originally named LatinSat, was initially operated by Aprize Argentina; however ownership of the constellation was later transferred to their US parent company AprizeSat.

The AprizeSat constellation is used for store-dump communications, and some satellites carry Automatic Identification System (AIS) payloads for Canadian company ExactEarth. The AprizeSat spacecraft were built by SpaceQuest, and each has a mass of 12 kilograms (26 lb).

Z9The UniSat-5 satellite, which will be operated by the Group of Astrodynamics for the Use of Space Systems (GAUSS) at Rome’s La Sapienza University, is the fifth – and so far largest – UniSat spacecraft to be launched. The last satellite, UniSat-4, was lost in the July 2006 Dnepr launch failure.

With a mass of 28 kilograms (62 lb), UniSat-5 will be used for a series of technology demonstration experiments including the planned release of eight subsatellites. The spacecraft is cubic in shape, with sides of 50 centimetres (1.6 feet).

In addition to the subsatellites, UniSat-5 carries two experiments. The first, GlioSat, will study how the space environment – particularly microgravity and radiation – affect glioblastoma cells.

The second instrument is the Digital Imaging Payload (DIP) which will use a Schmidt-Cassegrain telescope connected to an Elphel NC353L-369 camera to return high-resolution images of the Earth. Images will be downlinked using C and S band transponders.

The subsatellites deployed from UniSat-5 consist of four CubeSats and the first four PocketQube spacecraft to be launched. The satellite houses three Planted Elementary Platforms for Picosatellite Orbital Deploying, or PEPPODs, capable of housing the equivalent of three one-unit CubeSats each.

The first PEPPOD contained three single-unit satellites: ICube-1, HumSat-D and PUCP-Sat 1. The second deployer housed a single three-unit satellite, Dove 4. Italy’s e-str-2 satellite was intended to be carried on the mission; however it appears to have been removed leaving the third PEPPOD empty.

Three Morehead-Roma Femtosatellite Orbital Deployers (MRFSODs) were also mounted in the UniSat spacecraft. These were used to dispense a new class of miniaturised satellites; PocketQubes.

The standard was developed by Professor Bob Twiggs, a professor at Morehead State University and professor emeritus of Stanford University who previously invented the CubeSat standard in partnership with CalPoly’s Jordi Puig-Suari.

Like CubeSats, the PocketQube standard allows for satellites of varying size measured in standard units; however a single-unit, or 1p, PocketQube is one eighth the size of a single-unit CubeSat – with sides of five centimetres (two inches). Single, 1.5 and 2.5 unit satellites have been developed.

Z24ICube-1 is a single-unit CubeSat built and operated by Pakistan’s Institute of Space Technology. Primarily intended to give its developers experience of building and operating a satellite, ICube is expected to operate for three months. The Humanitarian Satellite Network Demonstrator, or HumSat-D, was developed by Spain’s University of Vigo.

A one kilogram spacecraft, it is expected to demonstrate technology for the planned Humanitarian Satellite Network – a constellation of store-and-forward communications satellites to provide a link to areas of the world without access to more developed systems.

The third single-unit CubeSat is PUCP-Sat 1, which will be operated by the Pontifical Catholic University of Peru (PUCP). It is the country’s first satellite. With a mass of 1.27 kilograms (2.8 lb), it is powered by ten solar cells charging a 1.5 amp-hour lithium ion battery.

The satellite carries temperature sensors which will be used to monitor its environment. It will also deploy a subsatellite, Pocket-PUCP, and relay temperature readings from the subsatellite back to Earth. Measuring 8.35 by 4.95 by 1.55 centimetres (3.3 x 1.9 x 0.6 inches) and with a mass of 97 grams (3.4 ounces), Pocket-PUCP is the smallest functional satellite ever launched.

UniSat’s final CubeSat, Dove 4, is one of two identical Dove spacecraft aboard the rocket, with the other loaded aboard an ISIPod deployer that was attached to the Dnepr’s upper stage. Dove satellites are precursor missions demonstrating technology for a planned constellation of Earth imaging satellites scheduled for launch later this year.

The Eagle 1 and 2 PocketQubes, also known as BeakerSat-1 and $50SAT respectively, are the first two prototypes of the PocketQube standard.

Developed at Morehead State University in Kentucky by a team working under Professor Twiggs, the two spacecraft will perform technology demonstration missions. BeakerSat-1 is a 2.5-unit satellite, measuring 5 by 5 by 15 centimetres (2 x 2 x 6 in), while $50SAT is a smaller 1.5p satellite – with a length of 10 centimetres (4 in). BeakerSat-1 will test a passive deorbit system while $50SAT is geared towards investigating the use of off-the shelf components in satellites.

QBScout-S1, or QubeScout-S1, is a 2.5-unit PocketQube built and operated by the University of Maryland. A 400-gram (14 oz) spacecraft it will demonstrate a sensor for tracking the satellite’s attitude from the position of the Sun, which will be used to monitor how the satellite’s inertia and rotation change while it is in orbit.

Wren is a single-unit PocketQube to be operated by STADOKO UG of Germany. The satellite will demonstrate an autonomous attitude control system which includes four plasma thrusters. The spacecraft will use gyroscopes, magnetometers and a small imager to determine its attitude, using the thrusters to manoeuvre to the correct attitude. The imager can also be used for Earth observation and astronomy.

In addition to those aboard UniSat-5, two further groups of nanosatellites, mostly CubeSats, were aboard the rocket. Three satellites werelaunched as part of the University of Toronto Institute for Aerospace Studies’ (UTIAS) Nanosatellite Launch Services programme.

Designated NLS-9, this payload consists of the Lem satellite for Poland’s Copernicus Astronomical Centre and Space Research Centre, WNISAT-1 for Japan’s Weather News Incorporated, and GOMX-1 for GOMSpace of Denmark.

Lem, which is also known as BRITE-PL1 or CanX-3C, is the third satellite to be launched as part of the Bright Target Explorer, or BRITE, programme. BRITE is an joint programme between Canadian, Polish and Austrian institutions. The University of Toronto is leading the programme, with the universities of Graz and Vienna in Austria and Poland’s Copernicus Astronomical Centre participating.

The programme has received funding from the Canadian Space Agency as well as the Polish and Austrian governments. Once complete the BRITE constellation will consist of six satellites: two Austrian, two Canadian and two Polish. The BRITE programme is aimed at studying the most luminous stars in the sky through photometric observation.

The programme’s goals are to help characterise the life cycles of these stars, and understand their roles in the formation of new stars.

The first two BRITE satellites to launch were the Austrian spacecraft, UniBRITE and TUGSAT-1. These were carried into orbit by India’s Polar Satellite Launch Vehicle, as secondary payloads on February’s launch of the SARAL oceanography satellite, in the process becoming Austria’s first satellites.

The next BRITE spacecraft to launch is the second Polish contribution, Heweliusz, which will be a secondary payload on a Chinese launch, currently planned for December.

Lem, which is named after writer Stanislaw Lem, was constructed by Poland’s Space Research Centre, using components and designs provided by UTIAS. Heweliusz, named after astronomer Johannes Heweliusz, was also built to designs provided by UTIAS, however many of the components were sourced by SRC.

Both satellites are based on Canada’s Generic Nanosatellite Bus, with masses of approximately ten kilograms. Lem has a design life of two years, and carries a small CCD telescope with a three centimetre (1.2-inch) aperture to conduct stellar observations.

A comparatively rare example of a two-unit CubeSat, GOMX-1 will rounds out the NLS-9 payloads.

A Danish spacecraft, it was constructed by GOMSpace and will be used for a technology demonstration mission. Its primary objective is to demonstrate whether a CubeSat can be used to receive Automatic Dependent Surveillance Broadcast (ADS-B) signals from aircraft flying over remote ocean regions where the signals cannot be tracked by conventional means.

The satellite will also be used to validate the CubeSat Space Protocol, an open-source communications software package which was partially tested by the AAUSat-3 spacecraft launched earlier this year aboard a PSLV. A camera is also aboard the spacecraft to return images of the Earth.

Z7Japan’s WNISAT-1 is a nanosatellite which will be operated by Weather News Incorporated. The satellite was constructed by Japanese consortium Axelspace, and has a mass of 10 kilograms (22 lb). It is cubic in shape with sides of 27 centimetres (10.6 inches).

Body-mounted solar cells will provide it with at least 12.6 watts of power and charge a 7.7 amp-hour battery. The spacecraft is three-axis stabilised by means of a gravity boom, magnetorquers and reaction wheels.

WNISAT-1 will be used to monitor weather over the Arctic shipping lanes. It carries visible-light and near-infrared imagers to observe conditions directly. The satellite also carries an atmospheric sounding experiment, using two lasers to probe the density of carbon dioxide in the atmosphere.

By observing from the ground how attenuated the beams are, the carbon dioxide concentration can be calculated. WNISAT-1 will operate for two years.

Z4The remaining fourteen payloads are CubeSats which are being launched through Dutch commercial provider Innovative Solutions in Space (ISIS or ISISpace), who also provided all of the CubeSat separation mechanisms, or ISIPods, for the launch – except those used by UniSat-5. One of the CubeSats, Triton 1, will be operated by ISIS itself.

A three-unit satellite, Triton will collect and relay Automatic Identification System (AIS) data from ships at sea. The satellite will be operated on behalf of ISIS’ subsidiary Innovative Data Services, which is investigating the development of a commercial constellation of such satellites.

CubeBug-2, also known as Manolito, is an Argentine amateur radio satellite which will follow up on the CubeBug-1, or El Capitán Beto, satellite launched earlier this year aboard a Chang Zheng 2D rocket. It will relay HAM radio messages, although it will use a different signal format and modulation to its predecessor.

A double-unit satellite, CubeBug will also be engaged in component testing. It will be operated by Argentina’s Ministry of Science, Technology and Productive Innovation.

Delfi-n3xt is a Dutch CubeSat for the Delft Technical University. A follow-up to the Delfi-C3 satellite launched in 2008, this triple-unit satellite carries propulsion, power generation and communications experiments.

Its primary objective is to test a micropropulsion system. Consisting of a cold-gas nitrogen thruster, the T3µPS system will generate 6 millinewtons of thrust with a specific impulse of 30 seconds. The satellite is carrying 2.4 grams (37 grains) of nitrogen for use as propellant.

Z22Dove 3 is a three-unit CubeSat. Along with Dove 4, which will be deployed by UniSat-5, it will be used by Planet Labs – formerly Cosmogia Incorporated – to demonstrate technology for the planned Flock-1 constellation of satellites.

Flock-1 will consist of 28 CubeSats and is due to be deployed from the International Space Station, which will be used to image the Earth at resolutions of up to three metres (10 feet).

The first two Dove satellites were launched two days apart in April, by Soyuz and Antares rockets. Dove 3 and 4 each have a mass of around 4.5 kilograms.

The First München Orbital Verification Experiment, First-MOVE, is being launched for Germany’s Technical University of Munich. The single-unit spacecraft will be used to demonstrate triple-junction Gallium Arsenide-Germanium solar cells, deployed on two panels. The satellite also carries a small CCD imager.

Z26FUNCube-1 is a British amateur radio satellite which was constructed by the UK branch of AMSAT. Due to licensing issues it will be registered as a Dutch spacecraft through a partnership with the Netherlands branch of AMSAT who also provided some of the components.

The satellite is designed for use by schools as part of an educational programme, and by amateur radio enthusiasts. It is a single-unit CubeSat. HiNCube was built and will be operated by Narvik University College in Norway. A one-unit CubeSat it carries a colour imager and eight temperature sensors – one in each corner of the satellite. The spacecraft will return images of the Earth and thermal data.

KHUSAT-1 and 2, also designated CINEMA-2 and 3 respectively, are South Korea’s contribution to the international CubeSat for Ion, Neutral, Electron, Magnetic fields, or CINEMA, programme. Developed by Korea’s Kyung Hee University, the satellites carry magnetometers produced by Imperial College London, in the United Kingdom.

The CINEMA programme is led by the University of California, who provided the CINEMA-1 satellite that was launched on an Atlas V rocket last year. NASA’s Ames Research Center is also involved in the programme, and launch services for CINEMA-1 were procured through NASA’s ELaNa CubeSat launch programme.

Three-unit CubeSats with masses of four kilograms (8.8 lb), the two KHUSATs carry two instruments; the Magnetometer from Imperial College (MAGIC) is used to characterise the Earth’s magnetic field in the satellite’s vicinity, while the Suprathermal Electrons, Ions and Neutrals (STEIN) experiment will detect energetic particles around the spacecraft.

Z99A single-unit CubeSat, NEE-02 Krysaor is Ecuador’s second satellite; following the NEE-01 Pegaso satellite which was launched aboard a Chinese Chang Zheng 2D rocket in April. After just under a month in orbit, communications with Pegaso were lost after the satellite passed close to the spent upper stage of a Tsyklon-3 rocket.

Built as a backup for Pegaso, Krysaor will be used by the Ecuadorian Space Agency for technology demonstration and educational outreach. Its experiments include tracking near-Earth objects and satellite debris.

OPTOS is a three-unit CubeSat which will be operated by the Spanish space agency, INTA. The satellite is based on a Pumpkin Incorporated CubeSat kit, and is designed for an operational lifespan of at least a year.

It has several technology demonstration objectives; validating new data-handling, logic and optical communications systems, testing a new controller network protocol, and demonstrating the use of composite materials in the construction of the satellite.

The spacecraft carries a small camera, the Athermalized Panchromatic Image Sensor (APIS) which will produce 1.8 megapixel images to demonstrate how exposure to space affects optical systems such as lenses.

Z55University of Wurzburg Experimental 3, or UWE-3, is a one-unit German CubeSat which will be used to test an attitude control system and data processing system. VELOX-P2 of Singapore’s Nanyang Technological University is another single-unit satellite which is intended to demonstrate systems produced by the university.

The satellite also carries an experimental sun sensor. VELOX-P1, which is loaded with a similar payload, has not been launched since it has been booked onto InterOrbital Systems’ Neptune rocket.

South Africa’s ZACube-1, which will be operated by the Cape Peninsula University of Technology, will be used for radar calibration and ionospheric research. A one-unit CubeSat, the spacecraft contains a high-frequency beacon which will be used for both mission objectives.

Research on the ionosphere can be conducted by studying how the signals are diffracted as they pass through it, while the beacon will also provide a regular signal that can be used to calibrate the SuperDARN inferometer at the South African National Antarctic Expedition station.

A prototype avionics package, Blok Perspektivnoy Avioniki 3 (BPA-3, lit. Advanced Avionics Unit 3), is also being carried by the Dnepr. The third in a series of avionics experiments flown on Dnepr missions, it follows the BPA-1 and 2 packages launched in 2010 and 2011 respectively.

The payload, manufactured by Ukrainian firm Hartron-Arkos, is attached to the third stage of the Dnepr, and is not designed to separate.

The Dnepr rocket, which was used for Thursday’s launch, is a converted R-36 missile; modified to carry satellites into orbit rather than to deploy nuclear warheads. The R-36 was developed in the 1960s as a two-stage intercontinental ballistic missile initially capable of delivering an 18 megaton nuclear warhead.

Later versions increased this capacity to a 25 megaton warhead or up to ten smaller bombs in Multiple Independently-Targetable Reentry Vehicles (MIRVs).

One variant, the R-36O, was designed as part of the Fractional Orbital Bombardment System (FOBS) to place a warhead into low Earth orbit and then deorbit it onto a target during the first revolution. FOBS-type weapons were subsequently banned under international treaty in 1979.

The specific variant of the R-36 upon which the Dnepr is based is the R-36MUTTH. Named the “SS-18 Mod.4” or “Satan” by Western intelligence it is also known as the RS-20B. The type was introduced in 1979 and scheduled to leave service in 2009, although some may still be operational.

The R-36MUTTH was replaced by the R-36M2, which remains in service. Dnepr rockets use the two-stage R-36MUTTH almost unmodified, with the missile’s post-boost stage – used to target the warheads – serving as the third stage of the orbital launch system.

Z33The DubaiSat-2 launch marked the nineteenth flight of a Dnepr; the rocket first flew in April 1999 carrying the British UoSAT-12 satellite.

In its previous eighteen launches it has suffered a single failure; a launch in July 2006 came down in Kazakhstan around 74 seconds after lifting off from the Baikonur Cosmodrome, after a hydraulic failure caused the vehicle to lose thrust vectoring in one of its first stage engine nozzles.

Eighteen satellites were aboard the rocket, which remains the record for the most payloads lost in a single mishap.

The Dnepr launched from Site 370/13 at Dombarovsky in south-west Russia. Near the town of Yasny, Dombarovsky is located close to Russia’s border with Kazakhstan. During the Cold War the site was a major missile base with sixty four silos for the R-36. Two interceptor squadrons were also based at the facility.

Dnepr ProcessingDnepr launches occur from minimally-modified R-36 silos; in addition to 370/13, two other facilities have been used by the Dnepr: Site 109/95 at the Baikonur Cosmodrome and Site 370/11 at Dombarovsky. Once the countdown reaches zero a hot gas generator was fired, ejecting the rocket from the silo.

Once the Dnepr has left its silo the gas generator separated from the aft end of the rocket, with a small motor mounted on one side firing to prevent it damaging the silo.

The first stage’s four RD-263 engines ignited with the rocket in mid-air at around 20 metres (66 feet) altitude. On at least one R-36 test flight the first stage failed to ignite, resulting in the rocket falling back into the silo and exploding. Once the engines are burning a set of rings which attach to the outside of the vehicle broke in halves and separated.

Dnepr OverviewThe first stage burned for around 98 seconds before it burnt out and separated. Approximately six seconds after staging the second stage ignited, burning its RD-0255 engine for 168 seconds.

The forward section of the payload fairing separated during this burn. Once the second stage burns out it was jettisoned, with the third stage reorienting itself to fly backwards.

The third stage of the Dnepr was derived from the Post-Boost Module developed for the R-36 missile. Originally designed to fine-tune the trajectories of multiple independently-targeted warheads, the unit has its engines mounted facing forwards.

To protect the satellites from the exhaust of the RD-869 engine, the rocket is fitted with a Gas Dynamic Shield, which covers the payloads until shortly before spacecraft separation.

The third stage is not restartable, so to avoid leaving debris in the same orbit as the payload spacecraft separation occurs while the engine is still burning, with the satellites being ejected from the back of the stage.

Due to the large number of satellites on Thursday’s mission, the Dnepr used a modified fairing which has been split into two platforms. DubaiSat-2 and STSAT-3 were mounted on the upper platform, with the remaining satellites and the CubeSat dispensers mounted to the lower platform. The gas dynamic shield sits atop the upper platform.

Launch ProfileThe payload fairing is split into three segments; the upper section separating into two halves during the ascent to orbit, while the lower half then separated along with the upper payload platform shortly before the satellites on the lower platform began to be deployed.

Once all thirty-two satellites have separated the upper stage continued to burn to depletion, leaving it in a higher orbit and minimising the risk of collision with one of the payloads.

The target orbit for DubaiSat-2 is a roughly circular sun-synchronous orbit at an altitude of around 600 kilometres (370 miles), with inclination of about 97.8 degrees. The other satellites will be placed into higher orbits.

Thursday’s launch was the sixty-eighth or sixty-ninth orbital attempt of the year – rumours of a failed Iranian launch in February have still not been confirmed – and the twenty-ninth to be conducted using a Russian or former Soviet rocket – including the Russo-South-Korean Naro-1 launch, a Soyuz launch from French Guiana and a failed Sea Launch mission using a Zenit-3SL.

Russia’s next launch will occur on Friday when a Rokot with a Briz-KM upper stage will place the European Space Agency’s three Swarm satellites into orbit.

The DubaiSat-2 mission was the second and final Dnepr launch to occur in 2013, following the successful deployment of Arirang-5 in August. The next Dnepr is scheduled to launch in April 2013, with the Deimos-2 remote sensing satellite and around twenty secondary payloads.

(Images via various satellite company sites and L2)

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