Minimize SSO-A

SSO-A (Sun Synchronous Orbit – A) — first Rideshare mission of Spaceflight Industries

Mission Management     Mission Integration    Launch    Payloads     References

In 2015, Spaceflight Industries of Seattle WA (simply referred to as 'Spaceflight'), initiated a dramatic new vision: buy a full Falcon 9 and fill it totally with Rideshare spacecraft. There was to be no ‘prime' satellite. There was the potential for ‘co-lead' status for a couple of customers, but otherwise it was an egalitarian mission. This mission was dubbed SSO-A for ‘Sun Synchronous Orbit – A" with "A" standing for the first of a planned series of such launches. 1)

The SSO-A mission takes the concept of a Rideshare – or ‘Multi Manifest Mission' – to a new level. A full Falcon 9 launch vehicle is being dedicated purely to Rideshare spacecraft – there is no ‘Primary' satellite that defines the mission (Figure 1).The approach is analogous to buying a seat on an airplane: everyone is leaving at the same time and going to the same place. No single passenger gets to change the departure time or destination. There are ‘Co-Lead' customer who get limited involvement in determining the launch date, as well as other enhanced services. In the air travel analogy, this would be equivalent to a special first-class ticket that would allow one or two passengers to ask for the departure to be delayed accommodating their schedule. For the SSO-A mission, there is only one commercial customer who has this special Co-Lead status.


Figure 1: SSO-A Launch depiction with Falcon-9 stage 2 of SpaceX (image credit: Spaceflight)

In all, there are 51 different customers, representing 14 different countries on the SSO-A mission. There are 16 MicroSats, as well as dozens of CubeSats ranging from 0.25U to 6U.

IPS (Integrated Payload Stack): The SSO-A configuration features an IPS. As shown in Figure 2, the IPS structure consists of multiple structural elements. The two major deployed elements designated the UFF (Upper Free Flyer) and LFF (Lower Free Flyer), as well as various sub-elements as shown in Figure 3.

UFF (Upper Free Flyer): The UFF consists of four primary structural elements:

1) ESPA (EELV Secondary Payload Adapter)

2) CubeStack

3) Hub

4) Top Section of the MPC (Multi Payload Carrier)

The ESPA is a standard aluminum ESPA ring with six port with 15" bolt pattern attachment points. This unit is built by Moog CSA Engineering of Mountain View, CA and has flown multiple times.

The CubeStack is an aluminum structure developed for the SSO-A configuration. It houses the UFF avionics, as well as providing port for up to five 6U-size CubeSat dispensers. It was built by LoadPath Engineering.

The Hub is similar to an ESPA Grande but is composite versus aluminum construction. It has six 24" diameter ports. It is built by Airbus Defense and Space (formerly CASA) in Madrid, Spain.

LFF (Lower Free Flyer): The LFF is a hexagonal aluminum structure designed to hold up to twelve 12U – or QuadPack – size CubeSat dispensers. It also includes avionics to autonomously separate all of the CubeSats on the LFF.


Figure 2: Illustration of a SSO-A IPS (integrated Payload Stack), image credit: Spaceflight)


Figure 3: SSO-A structural elements (image credit: Spaceflight)

MPC (Multi Payload Carrier): The MPC is a load-carrying composite structure. There is a separation mechanism between the lower and upper halves of the MPC. This separation join allows the UFF to be released and to then autonomously deploy the spacecraft attached to it. There are also four platform on the MPC on which four microsats are mounted and deployed. The MPC is an adaption of the ASAP-S multiple payload structure previously built and flown on Soyuz launch vehicles by Arianespace.

The overall mission scenario is shown in Figure 4. Once the UFF and LFF are separated by the launch vehicle, their avionics power up, initialize, and begin separating the spacecraft in a predetermined sequence.



Figure 4: SSO-A deployment sequence from Falcon-9 (image credit: Spaceflight)

The UFF and LFF both have S-band transmitters for downlinking status to the ground. This data will be received by Spaceflight's ground station network and linked back to the Mission Operations Center (MOC) at Spaceflight's main office in Seattle, WA. In addition, the UFF is utilizing a Globalstar relay to provide a GPS positional solution and telemetry data throughout the mission. This data will also be linked from the Globalstar ground station network back to the MOC.

The telemetry includes verification indicators for each spacecraft separation. Switches on the deployers – separation systems and CubeSat dispensers – are monitored by the UFF and LFF avionics transmitted to ground stations to provide verification of spacecraft separation. Figure 6 shows the preliminary ground track prediction for the first three orbits along with the location of the three Spaceflight ground stations.

After separation from the F9 upper stage, the UFF and LFF autonomously deploy their spacecraft. At the time of the writing, the details of the final separation sequence are being analyzed. A significant challenge in this analysis is to minimize the potential for recontact between objects and creating undesirable space debris, To do this, a complex analysis and simulation is being employed to evaluate the relative dynamics between all of the separated objects. This involves Monte Carlo analyses of multiple parameters that can affect the orbital parameters, such as separation spring variability, mass uncertainty, and free-flyer body rotation rates.


Figure 5: Illustration of the launch sequence (image credit: Spaceflight)

The UFF and LFF do not have active attitude control, so the body rates are minimized by balancing the inertias imparted by the spacecraft separations. The separation sequence attempts to separate spacecraft with similar imparted inertias from opposite sides of the IPS, balancing the imparted body rates.

The general order of the UFF deployment sequence is:

1) Co-Lead Microsats

2) Rideshare Microsats

3) CubeSats

Nominally, separations are timed at 5 minutes apart to allow more time for the spacecraft to accrue separation distance. However, some cases there are separations as short as 15 seconds and the avionics can accommodate simultaneous separations, if needed. All told, the UFF separation sequence lasts until approximately 4 hours and 40 minutes after launch and the LFF separation sequence goes until L+ 5 hours.

The final separation sequence will be defined by the analysis of the spacecraft on the final manifest, running the Monte Carlo conjunction analysis to confirm an adequately low probability of recontact between all of the separated objects. The acceptable threshold was determined via coordination with the FCC as part of getting the frequency approval process for the UFF and LFF.


Figure 6: SSO-A preliminary initial ground track (image credit: Spaceflight)


Mission Management:

Making sure the 80+ spacecraft that have been manifested on SSO-A are ready and able to be integrated with the IPS is a substantial effort. To accomplish this as efficiently as possible, Spaceflight has developed a host of standardized processes and methods to streamline the effort.

ICD (Interface Control Document): One of the primary tools used to manage the integration of spacecraft onto launch vehicles in the ICD. For a typical single-to-few spacecraft mission, this can be handled with a typical document processed in MS Word or similar. Reviews and approvals have normally been handled by distribution of discrete review copies of the document, getting back comments and making the changes.

Ultimately, the final document is routed for signature approvals. However, trying to employ this process for the multitude of customers on SSO-A would quickly get unwieldy. Therefore, Spaceflight adopted the online-accessible Jama Software requirements management tool. ( Spaceflight has also adopted Jama for all of their internal requirements documentation, allowing a direct connection between customer requirements from an ICD to system requirements. An ICD or other requirement document is called a ‘Project' in Jama.

Using Jama, the Mission Management team created ICDs that can be reviewed by each customer via a browser-based interface. Each ICD requirement can be reviewed and approved discretely on a real-time basis. Rather than issuing new releases of a document to circulate for review, progress of the ICD toward completion can be tracked statistically based on how many of the requirements have been reviewed – and ultimately approved – by each participant. Each participant can be designated as either a review or approver. Reviewers can read the document and make comments on each requirement or section of the ICD. Approvers can to the same but have the additional ability to approve or reject each item. Approving is a simple matter of clicking a ‘check mark' box. Alternatively, an ‘X' can be clicked, indicating the item needs more work. All changes are maintained in the Jama database, allowing one to trace the evolution of the ICD.

To avoid reinventing the wheel and maintaining consistency, Spaceflight developed standardized ICD templates within Jama. Because of the differences in complexity and means of the deployment, separated ICD templates were created for MicroSats and CubeSats. When a new customer was signed for the mission, it became a relatively simple matter to copy the template and edit it with spacecraft-specific information. Moreover, Jama has the ability to ‘push' updates to properly linked projects. Therefore, when revisions are identified that apply to all spacecraft on the mission, they can be pushed out for incorporation in all the linked ICD.

Finally, Jama allows verification artifacts to be directly associated with requirements. The definition of the artifact can be included in the same Jama project as the requirements. The actual artifact (i.e. test reports, analyses, etc) documentation can then be linked to the artifact item in the ICD, providing robust documentation of the ICD requirements verifications.

Regulatory Requirements: Complying with regulations established by Government organizations is not exactly rocket science, but can be a major impediment to getting launched. Approvals are required from multiple agencies. These approvals include radio frequency approval from the FCC (Federal Communications Commission) Earth imaging from NOAA (National Oceanic and Atmospheric Administration), and transport to the launch Range from DoT (Department of Transportation). Additionally, the FAA (Federal Aviation Administration) licenses the commercial Falcon 9 launch vehicle via SpaceX.

Each spacecraft organization coordinates their own approvals. However, Spaceflight also needs to gain the appropriate approvals for the stack elements, for transport, as well the UFF and LFF in space since they are free-flying objects. To do this, information from all of the spacecraft is needed.

DoT special permits are typically needed for transporting spacecraft which have lithium ion (Li-Ion) batteries and/or pressure vessels over US streets and highways. Since most spacecraft are now using Li-Ion batteries, these spacecraft also require DoT special permits. Spaceflight is integrating most of these spacecraft at their Auburn, WA integration facility and then subsequently transporting the stack elements to VAFB (Vandenberg Air Force Base). Therefore, they need to get a special permit which encompasses all of the constituent spacecraft, as well as the IPS elements. Evidence of all of the individual spacecraft permits are needed to accomplish this.

Even more vital is FCC licensing. As part of the FCC frequency approval, they also review orbital debris policy compliance. This includes debris mitigation on orbit (recontact & conjunction analyses), reentry within 25 years, and reentry hazards at end of mission. For this, specific spacecraft information is included in the supporting analysis and application. Given the large number of spacecraft on SSO-A, this is not a trivial effort. As mentioned previously, a complex Monte Carlo separation and conjunction analyses was conducted for all of the separating objects on the mission. Similarly, a reentry debris hazard analysis was completed for the UFF and LFF structures and subsystems that remained after spacecraft separation. The results of these analyses, along with other required documentation, were reviewed with and submitted to the FCC for frequency approval.

Getting frequency approvals is critical to facilitate the launch. When SpaceX applies for their FAA license to launch, they submit a list of all spacecraft on the mission. The FAA initiates an interagency review to assure all applicable US Government agencies do not have concerns with any elements of the mission. As part of this review, the FCC provides confirmation that all US-origin spacecraft have the proper licensing. If just one spacecraft on the mission – even a single CubeSat – does not have a license, the FAA will not issue the launch license. Therefore, Spaceflight requires that all spacecraft on the mission – domestic, foreign, or US Government – all provide evidence of proper licensing. If a spacecraft does not provide the necessary proof, they will not be integrated onto the launch vehicle.

Spaceflight also coordinates closely with JSpOC (Joint Space Operations Center) of the United States Strategic Command (USSTRATCOM) which, among other operational duties, monitors objects in Earth orbit. Although it is not a specific regulatory requirement, given the number new objects being delivered to Earth orbit by SSO-A, it was deemed important by Spaceflight to be good space-citizens and assist JSpOC in identifying all of the spacecraft to be launched.


Mission Integration

Integration for the SSO-A mission is occurring at two primary locations: Spaceflight's Integration Facility in Auburn, WA and the SpaceX PPF (Payload Processing Facility) at Vandenberg AFB, CA.

Spaceflight Integration Facility: The development and integration of the mission elements prior to the start of spacecraft integration happens at the Spaceflight Integration Facility. This includes receiving and inspection of all incoming hardware, such as structures, avionics, cable harnessing, spacecraft separations systems, and CubeSat deployers. It also includes the effort to build-up and functionally test the avionics and subsystems.

The Auburn facility was built-out primarily to support the requirements for the integration of SSO-A. Because of the large structures and IPS height fully stacked, a facility was required with a higher ceiling than Spaceflight's prior location in Tukwila, WA could provide. .It includes a larger and more capable certified ISO 8 cleanroom (<100,000 0.5 µm particles/ft3) clean room Figure 7). The new facility incorporates a 3-ton bridge crane to move hardware and integrate dozens of discrete spacecraft The cleanroom has an airlock for moving hardware in and out, a gowning room, and an electrostatic dissipative floor. The air is constantly scrubbed by filters and its conditions are controlled to keep humidity and temperature within required levels. There is also a portable cleanroom tent capable of ISO 7 (<10,000 0.5 µm particles/ft3) for smaller integration work, such as CubeSat-to-dispenser integration. The facility also includes lab bench for testing, allowing testing of new software/firmware on non-flight hardware before testing it on the flight hardware in the cleanroom environment.


Figure 7: Spaceflight's Auburn Integration Facility Cleanroom (image credit: Spaceflight)

IPS Integration and Test: Spaceflight conducts many layers of avionics testing, over the life of the program, from bench-level testing through full system-level, to make sure the UFF and LFF are ready for customer payload integration, flight, and eventual operations. All hardware received from vendors is subject to receiving inspection, to make sure it was built up to specifications. Software is tested incremental, getting more flight-like at each step, until ultimately testing the actual mission scripts that will run during launch. The final tests look at the entire mission duration, from going to internal power on the launch pad, the moment of separation from the launch vehicle, through our on-orbit passes over Spaceflight ground stations. The Mission Simulation Tests can last as long as 16 hours. During these tests data collection and dissemination is simulated, sending the data to the mission management team who will eventually send those data to customers during post-launch operations, so they can locate and communicate with their spacecraft.

Figure 8 shows the flow of how the four major structures come together. The LFF and the upper segment of the UFF are shown in Figure 9 during integration testing. This mechanical process was demonstrated prior to the final integration of each sub-element into flight configuration. The stack up was also previously demonstrated, in the Fall of 2017, in preparation for a modal survey that was successfully completed on the IPS structure.


Figure 8: SSO-A major structures mechanical integration flow (image credit: Spaceflight)

Spacecraft Integration: After the IPS and all Spaceflight elements are all fully integrated and tested, the Customer spacecraft arrive for integration and preparation for launch. This starts 60 days prior to launch and continues for almost three weeks. With an unprecedented number of customers and spacecraft, careful coordination and scheduling of integration activities is imperative. The Assembly, Integration and Test engineers' preliminary schedule is planned with ½ day fidelity. For the final schedule, integration is being planned to hourly increments. As an added challenge, the timing of customer integration need to factor in which customers are integrating at the same time. Some customer may be competitors, so they would prefer not to reveal any details about their systems to each other. Similarly, there are US Government spacecraft that need to avoid access by foreign nationals. These factors, and more, were considered in creating the detailed integration schedule.


Figure 9: Integration and test prior to spacecraft integration (image credit: Spaceflight)

Launch: A launch of the SSO-A rideshare mission of Spaceflight is expected in November 2018 on a SpaceX Flacon-9 Block 5 vehicle from VAFB (Vandenberg Air Force Base) in California. 2) 3)

Engineers working for Spaceflight, a Seattle-based launch services company, are in the final steps of preparing for the first launch of new robotic free flyers carrying more than 70 small government and commercial satellites into polar orbit later this year aboard a dedicated flight of a SpaceX Falcon 9 rocket.

Most of the satellites on the SSO-A mission, which include 15 microsatellites and 56 CubeSats, will be installed on two free flyers at Spaceflight's facility in Auburn, Washington, near Seattle, officials said.

Orbit: Sun-synchronous circular orbit with an altitude of 575 km, inclination of ~98º, LTDN (Local Time of Descending Node) of 10:30 hours.


Figure 10: Artist's illustration of the SSO-A mission's free flyers separating from the upper stage of SpaceX's Falcon 9 rocket (image credit: Spaceflight)


Figure 11: Artist's illustration of the SSO-A mission's free flyers separating from the upper stage of SpaceX's Falcon-9 rocket (image credit: Spaceflight)


List of payloads on the Spaceflight SSO-A rideshare mission

The layout of the list follows the alphabetical order of missions as presented on the Wikipedia page "2018 in spaceflight" — as well as with the help of Gunter Krebs's short descriptions at /

• AISTechSat, a 6U CubeSat for Earth observation of AISTech (Access to Intelligent Space Technologies), Barcelona, Spain.

• Al Farabi-2, a CubeSat technology demonstration mission of the Al-Farabi Kazakh National University, Kazakhstan.

• Astrocast, a 3U CubeSat technology demonstration mission of Astrocast, Switzerland, dedicated to the Internet of Things (IoT)

• Audacy Zero, a 3U CubeSat technology demonstration mission of Audacy, Mountain View, CA

• BeeSat-5 to -8 (Berlin Experimental and Educational Satellite) of TU Berlin, a picosatellite mission consisting of four 0.25 CubeSats.

• BlackSky-2, a microsatellite (55 kg) of BlackSky Global which will provide 1 m resolution imagery with improved geolocation accuracy.

• BRIO, a 3U CubeSat of SpaceQuest Ltd. of Fairfax, VA to test a novel communications protocol that uses SDR (Software Defined Radio).

• Capella-1, a 12U CubeSat of Capella Space, San Francisco, CA featuring a X-band SAR (Synthetic Aperture) payload.

• Centauri-2, a 3U CubeSat of Fleet Space Technologies, Adelaide, South Australia. Demonstration of IoT technologies.

• COPPER (Close Orbiting Propellant Plume and Elemental Recognition) CubeSat of Saint Luis University, Saint Louis, MO, USA.

• CSIM-FD (Compact Spectral Irradiance Monitor-Flight Demonstration), a 6U CubeSat of LASP (Laboratory for Atmospheric and Space Physics) at the University of Boulder, CO, USA. The goal is to measure solar spectral irradiance to understand how solar variability impacts the Earth's climate and to validate climate model sensitivity to spectrally varying solar forcing.

• Eaglet-1, the first 3U CubeSat of OHB Italia SpA for Earth Observation.

• Elysium Star-2, a 1U CubeSat of Elysium Space providing space burial services.

• ESEO (European Student Earth Orbiter) sponsored by ESA, a microsatellite of ~40 kg with 6 instruments aboard.

• Eu:CROPIS (Euglena and Combined Regenerative Organic-Food Production in Space), a minisatellite (250 kg) of DLR, Germany. The objective is to study food production in space in support of future long-duration manned space missions (life sciences). The main payloads are two greenhouses, each maintained as a pressurized closed loop system, simulating the environmental conditions of the Moon or of Mars.

• eXCITe (eXperiment for Cellular Integration Technology), a DARPA (Defense Advanced Research Projects Agency) mission to demonstrate the 'satlets' technology. Satlets are a new low-cost, modular satellite architecture that can scale almost infinitely. Satlets are small modules that incorporate multiple essential satellite functions and share data, power and thermal management capabilities. Satlets physically aggregate in different combinations that would provide capabilities to accomplish diverse missions.

• ExseedSat-1, a 1U CubeSat mission by the Indian company Exseed Space. The goal is to provide a multifunction UHF/VHF NBFM (Narrow Band Frequency Modulation) amateur communication satellite.

• FalconSat-6, a minisatellite (181 kg) of the USAFA (U.S. Air Force Academy) and sponsored by AFRL. FalconSat-6 hosts a suite of five payloads to address key AFSPC (Air Force Space Command) needs: SSA (Space Situational Awareness) and the need to mature pervasive technologies such as propulsion, solar arrays, and low power communications.

• Flock-3, three 3U CubeSats of Planet Labs to provide Earth observation.

• Fox-1C, a radio amateur and technology research 1U CubeSat developed by AMSAT and hosting several university developed payloads.

• Hawk, a formation-flying cluster of three microsatellites (13.4 kg each) of HawkEye 360, Herndon, VA, USA. The goal is to demonstrate high-precision RFI (Radio Frequency Interference) geolocation technology monitoring.

• Hiber-2 is 6U CubeSat pathfinder mission of Hiber Global, Noordwijk, The Netherlands, for Hiber Global's planned (IoT) communications CubeSat constellation.

• ICE-Cap (Integrated Communications Extension Capability), a 3U CubeSat of the US Navy. The objectives are to demonstrate a cross-link from LEO (Low Earth Orbit) to MUOS (Mobile User Objective System) WCDMA (Wideband Code Division Multiple Access) in GEO (Geosynchronous Orbit). The objective is to send to users on secure networks.

• ICEYE-X2, a X-band SAR (Synthetic Aperture Radar) microsatellite (<100 kg) of Iceye Ltd, a commercial satellite startup company of Espoo, Finland.

• ITASAT-1 (Instituto Tecnológico de Aeronáutica Satellite), a Brazilian 6U Cubesat (~8kg) built by the Instituto Tecnológico de Aeronáutica (ITA). A former rescoped microsatellite mission.

• JY1-Sat, a 1U CubeSat of Jordan developed by students of various universities. The satellite will carry a UHF/VHF amateur radio.

• KazSTSAT (Kazakh Science and Technology Satellite), a microsatellite (~100 kg) of Ghalam LLP, Astana, Kazakhstan. Developed by SSTL on a SSTL-50 platform including an SSTL EarthMapper payload designed for global commercial wide-area imaging with a resolution of 17.5 m on a swath of 250 km.

• KNACKSAT (KMUTNB Academic Challenge of Knowledge SATellite) of Thailand, a 1U technology demonstration CubeSat, the first entirely Thai-built satellite, developed by students of King Mongkut's University of Technology North Bangkok (KMUTNB). Use of an amateur radio for communication.

• Landmapper-BC (Corvus BC 4), a 6U CubeSat (11 kg) of Astro Digital (formerly Aquila Space), Santa Clara, CA, USA. The satellite features a broad coverage multispectral (Red, Green, NIR) imaging system with a resolution of 22 m.

• MinXSS-2 (Miniature X-ray Solar Spectrometer-2), a 3U CubeSat(4 kg) of LASP (Laboratory for Atmospheric and Space Physics) at the University of Colorado at Boulder,CO, USA. The objective is to study the energy distribution of solar flare SXR (Soft X-ray) emissions and its impact on the Earth's ITM (Ionosphere, Thermosphere, and Mesosphere) layers. — MinXSS-1 was launched on 06 December 2015 onboard of Cygnus CRS-4 to the ISS, were it was deployed into orbit on 16 May 2016. It reentered Earth's atmosphere on 6 May 2017.

• NEXTSat-1, a multi-purpose microsatellite (~100 kg) of Korea designed and developed at SaTReC (Satellite Technology Research Center) of KAIST (Korea Advanced Institute of Science and Technology). The goal is to conduct scientific missions such as star formation and space storm measurements and also technology demonstration in space. Instruments: ISSS (Instrument for the Study of Space Storms) developed at KAIST to detect plasma densities and particle fluxes of 10 MeV energy range near the Earth. NISS (NIR Imaging Spectrometer for Star formation history), developed at KASI (Korean Astronomy and Space Science Institute).

• Orbital Reflector, a 3U CubeSat project (4 kg) of the Nevada Museum of Art and artist Trevor Paylon. The Orbital Reflector is a 30 m sculpture constructed of a lightweight material similar to Mylar. On deployment, the sculpture self-inflates like a balloon. Sunlight reflects onto the sculpture making it visible from Earth with the naked eye — like a slowly moving artificial star as bright as a star in the Big Dipper.

• ORS-7 (Operationally Responsive Space 7), two 6U CubeSats (-7A and -7B) of the USCG (US Coast Guard) in cooperation with DHS (Department of Homeland Security), the ORS (Operationally Responsive Space Office) of DoD, and NOAA. The objective is to detect transmissions from EPIRBs (Emergency Position Indicating Radio Beacons), which are carried on board vessels to broadcast their position if in distress.

• PW-Sat 2 (Politechnika Warszawska Satellite 2), a 2U CubeSat of the Institute of Radioelectronics at the Warsaw University of Technology, Warsaw, Poland. The objective is to demonstrate a deorbitation system - a drag parachute opened behind the satellite - which allows faster removal of satellites from their orbit after it completes its mission.

• RAAF-M1 (Royal Australian Air Force-M1), an Australian 3U CubeSat (~4 kg) designed and built by UNSW (University of New South Wales) for the Australian Defence Force Academy, Royal Australian Air Force. RAAF-M1 is a technology demonstration featuring an AIS receiver, and ADS-B receiver, an SDR (Software Defined Radio).

• RANGE-A and -B (Ranging And Nanosatellite Guidance Experiment), two 1.5 CubeSats of Georgia Tech (Georgia Institute of Technology), Atlanta, GA, USA, flying in a leader-follower formation with the goal of improving the relative and absolute positioning capabilities of nanosatellites.

• ROSE-1, a 6U CubeSat of Phase Four Inc., El Segundo, CA, USA. ROSE-1 is an experimental spacecraft designed to provide an orbital test-bed for the Phase Four RFT (Radio Frequency Thruster), the first plasma propulsion system to fly on a nanosatellite.

• SeaHawk, two 3U CubeSats of UNCW (University of North Carolina, Wilmington), NC. The goal is to measure the ocean color in project SOCON (Sustained Ocean Observation from Nanosatellites). They are considered prototypes for a larger constellation. The SOCON project is a collaboration between Clyde Space Ltd (spacecraft bus), the University of North Carolina Wilmington, Cloudland Instruments, and NASA/GSFC (Goddard Space Flight Center).

• SkySat-14 and -15. Planet of San Francisco has 13 SkySats in orbit. The commercial EO satellites were built by Terra Bella of Mountain View, CA, which Planet acquired from Google last year. At the time of the purchase, there were 7 SkySats in orbit. On 31 October 2017, Planet launched an additional six on a Minotaur-C rocket. The 100 kg SkySats are capable of sub-meter resolution – making them the most powerful in the constellation. Customers can request to have these high-resolution satellites target their locations of interest.

• SNUGLITE, a 2U CubeSat designed by the SNU (Seoul National University) for technology demonstrations and amateur radio communication.

• SpaceBEE, four picosatellites of Swarm Technologies (a US start-up), built to the 0.25U form factor to make up a 1U CubeSat.

• STPSat-5 is a science technology minisatellite of the US DoD STP (Space Test Program), managed by the SMC of the USAF. STPSat-5 will carry a total of five technological or scientific payloads to LEO (Low Earth Orbit) in order to further the DoD's understanding of the space environment. The satellite was built by SNC (Sierra Nevada Corporation) on the modular SN-50 bus with a payload capacity of 50-100 kg and compatible with ESPA-class secondary launch adaptors.

• THEA, a 3U CubeSat built by SpaceQuest, Ltd. of Fairfax, VA to demonstrate a spectrum survey payload developed by Aurora Insight, Washington DC. The objective is to qualify Aurora's payload, consisting of a proprietary spectrometer and components, and demonstrate the generation of relevant measurements of the spectral environment (UHF, VHF, S-band). The results of the experiment will inform future development of advanced instrumentation by Aurora and component development by SpaceQuest.

• VESTA is a 3U CubeSat developed at SSTL in Guildford, UK. VESTA is a technology demonstration mission that will test a new two-way VHF Data Exchange System (VDES) payload for the exactEarth advanced maritime satellite constellation. Honeywell Aerospace is providing the payload. VESTA is a flagship project of the National Space Technology Program, funded by the UK Space Agency and managed by the Center for EO Instrumentation and Space Technology (CEOI-ST).

• VisionCube-1, a 2U CubeSat designed by the Korea Aerospace University (KAU) to perform research on Transient Luminous Events in the upper atmosphere. The image processing payload consists of a multi-anode photon multiplier tube(MaPMT), a camera, and a real-time image processing engine built by using SoC (System-on-Chip) FPGA technologies.

• ZACube-2 (South African CubeSat-2), a 3U CubeSat of F'SATI (French South African Institute of Technology) at CPUT (Cape Peninsula University of Technology), Cape Town, South Africa (in collaboration with SANSA and Stellenbosch University).The payloads include a medium resolution matrix imager and a number of communication subsystems. The prime objective of ZACUBE-2 is to demonstrate AIS (Automatic Identification System) message reception using its SDR-based payload. The launch of ZACube was planned for 2018 on an Indian PSLV rocket but has been moved to a Falcon-9 v1.2 vehicle from VAFB.


Of the 71 satellites booked on the SSO-A mission, more than 30 are from international customers, according to Spaceflight. Organizations from 18 countries have payloads on the SSO-A mission: the United States, Australia, Italy, Netherlands, Finland, South Korea, Spain, Switzerland, United Kingdom, Germany, Jordan, Kazakhstan, Thailand, Poland, Canada, South Africa, Brazil, and India (Ref. 2).


Figure 12: This infographic released by Spaceflight illustrates the types of payloads booked on the SSO-A mission (image crdit: Spaceflight)

1) "Scott Schoneman, Jeff Roberts, Adam Hadaller, Tony Frego, Kristen Smithson, Eric Lund, "SSO-A: The First Large Commercial Dedicated Rideshare Mission," Proceedings of the 32nd Annual AIAA/USU Conference on Small Satellites, Logan UT, USA, Aug. 4-9, 2018, paper: SSC18-II-04, URL:

2) Stephen Clark, "Spaceflight preps for first launch of unique orbiting satellite deployers," Spaceflight Now, 23 August 2018, URL:

3) Jeff Foust, "Spaceflight gears up for dedicated Falcon 9 launch," Space News, 6 August 2018, URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (

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