LituanicaSAT-2 (LS-2) is 3U CubeSat in-orbit technology demonstration mission led by Vilnius University. The mission is a part of a network of 50 nanosatellites called "QB50" that will be launched together in 2017. 1) 2)
The "QB50" project is led by the Von Karman Institute (VKI) for fluid dynamics (Brussels, Belgium), under the European Commission's research and innovation program FP7 . The project involves 50 institutions all over the world each building their CubeSats that will be launched into space during the "QB50" mission.
The mission objectives are:
• In orbit demonstration of propulsion system prototype developed by Vilnius University and NanoAvionics. The experiment is to demonstrate the orbital maneuvering and drag compensation capabilities of a 3 kg CubeSat using an integral green monopropellant micro-thruster powerful enough to perform impulsive Hohman orbital transfer, orbit shape corrections or change of inclination. The idea behind this experiment is to increase TRL of small-satellite micro propulsion which would be developed as commercial product.
• The QB50 mission science objective is to carry out a long term measurements of key parameters and constituents in yet largely unexplored lower thermosphere and ionosphere.
• Test of the data uplink and downlink capability between CubeSats and RPAS (Remotely Piloted Aircraft Systems). The purpose of the experiment is to determine technical challenges associated with RPAS and CubeSat radio communication and prove the feasibility of such networks.
The science objective of the mission is to carry out long term measurements of key parameters and constituents in yet largely unexplored lower thermosphere and ionosphere. The satellites will be deployed into a circular polar orbit at an altitude higher than 300 km. NanoAvionics JSC has been contracted by Vilnius University to build a satellite platform and a propulsion system for LituanicaSAT-2.
The propulsion system features a green monopropellant microthruster able to perform high impulse orbital maneuvers and drag compensation capabilities for a small scale satellite. The system is designed to provide 0.3 N thrust and up to 200 m/s of ΔV. It is powerful enough to perform impulsive Hohman orbital transfer, orbit shape corrections or even change of inclination for a 3 kg satellite. The fuel used is a green monopropellant fuel blend based on ADN (Ammonium Dinitramide).
LituanicaSAT-2 is a 3U CubeSat, consisting of 3 main modules: a science unit - FIPEX sensor, a functional unit - NanoAvionics Command and Service module, plus a power unit and an experimental unit the "green" propulsion system.
The system bus - NanoAvionics "SatBus 3C1" - is integrated on a single PCB (Printed Circuit Board). The SatBus 3C1 is a highly integrated small satellite main bus containing a 3 in 1 functionality:
- on-board computer
- attitude determination & control subsystem
- communication subsystem
It is designed to be compatible with the CubeSat standard, but also appropriate for small sized spacecraft missions. JSC NanoAvionics has been contracted by Vilnius University to build a satellite platform and a propulsion system for LituanicaSAT-2. Next to the QB50 mission science objectives, the LituanicaSAT-2 mission is particularly important for NanoAvionics, since the innovative propulsion system prototype for small satellites developed by NanoAvionics will be tested during this mission. The fuel used is a LMP103S green monopropellant fuel blend developed by ECAPS (Sweden).
Figure 1: Photo of the SatBus 3C1 PCB (image credit: LS-2 team)
• OBC (On-Board Computer) and data handling subsystem based on ARM Cortex-M4F microcontroller with memory for science and housekeeping data storage (2 x 16 MB SPI NOR-flash data memory), as well as I2C, CAN and UART data interfaces for satellite payload and EPS. The module also contains an in-orbit firmware reload function.
- A SEU (Single Event Upset) software solution has been developed by Kubos to correct errors that can occur in the satellite's memory due to radiation. 3)
• ADCS (Attitude Determination and Control Subsystem) enabling de-tumbling, nadir and inertial pointing control modes, featured with Kalman Filter for attitude estimation. Inputs: sun sensors, 3-axis magnetometer, 3-axis gyroscope, 3-axis accelerometer. Outputs: estimated attitude, orbital position, magnetorquer control signals (x3). The module also contains an in-orbit firmware reload function.
Two magnetorquer rods and one coil are used to generate B-dot rate damping torque. External fine sun sensors are used to determine the angle of the incident sun rays with an accuracy down to ±0.5º.
• RF communications: Use of a half-duplex radio UHF communication subsystem providing a downlink rate of 9.6 kbaud. Compatibility with the AX.25 data protocol. The Rx sensitivity in the 9.6 kbaud band is -120 dBm. The RF output power = 2W. The subsystem provides a reconfigurable function on orbit.
• The bus structure is made of 7075 aluminum alloy with hard anodized surfaces. the structure also includes deployment elements to accommodate the solar panels. The in-house developed bus structure is a machined skeleton type and provides rigid structural support for the propulsion subsystem.
• EPS (Electrical Propulsion Subsystem): The EPS features 4 fixed and 4 deployable mono-crystalline silicon solar panels custom designed and manufactured by NanoAvionics. The panels have an efficiency of 20% which provides the voltage and power outputs to charge the batteries. A COTS system is used featuring a 2.6 Ah lithium ion battery pack.
The solar cells are cut to custom shapes, tailored to the solar panel layout and cutouts to accommodate as much surface area as possible. The solar panels deploy to form space dart configuration which provides passive aerodynamic stabilization with velocity vector pointing accuracy of about ±5º.
• Propulsion subsystem: The experimental propulsion subsystem is designed to provide 0.3 N thrust and up to 200 m/s of ΔV. The fuel used is a contemporary green monopropellant fuel blend based on ADN (Ammonium Dinitramide). It provides an Isp of 252 s , has a density of 1.24 g/cm3 with a chamber temperature of 1600ºC. Key fuel selection factors were non-toxicity, stability and benign handling properties, at the same time giving very similar or even better performance as the conventional hydrazine monopropellants. The current TRL (Technology Readiness Level) is at level 5/6.
Figure 2: Image of the propulsion subsystem prototype (image credit: University of Vilnius)
Figure 3: Illustration of the deployed LituanicaSAT-2 nanosatellite (image credit: University of Vilnius, NanoAvionics)
Launch: A launch of the LituanicaSAT-2 nanosatellite as a secondary payload is scheduled for late May 2017 on the PSLV-C38 vehicle of ISRO from SDSC (Satish Dhawan Space Center), India. The primary payload on this flight is CartoSat-2E. 4)
Orbit: Sun-synchronous near-circular orbit, altitude of 640 km, inclination = 97.8º, LTDN (Local Time on Descending Node) at 9:30 hours.
• CE-SAT-1 (Canon Electric Satellite-1), a microsatellite of Canon Electronics Space Technology Laboratory, Japan.
• Max Valier, a nanosatellite (16 kg) of the "Max Valier" school Bolzano and the "Oskar von Miller" school Merano, in South Tyrol, Italy.
• 3 Diamond nanosatellites (Blue, Green, Red) of Sky and Space Global, UK, developed by GomSpace ApS of Denmark. The three 3U CubeSats (each 6 kg) are pathfinders for Sky and Space Global's 200 Satellite LEO constellation.
• Venta-1, a nanosatellite (7.5 kg) of Ventspils University, Latvia, developed by Ventspils University College in cooperation with Ventspils High Technology Park, Bremen University of Applied Sciences and OHB Systems.
• PicSat, a 3U CubeSat mission of the Paris Observatory within the High Angular Resolution Astronomy group at LESIA - to observe the exoplanetary transits of the giant planet β Pictoris, expected some time between July 2017 and June 2018.
• Aalto-1, a Finnish student nanosatellite (3U CubeSat) of Aalto University, Aalto, Finland.
• COMPASS-2 (DragSail CubeSat), a 3U CubeSat of FH Aachen, Germany (technology demonstration nanosatellite). COMPASS-2 is part of the QB50 constellation.
• InflateSail, a 3U CubeSat of SSC (Surrey Space Centre) at the University of Surrey, UK (technology demonstration nanosatellite). Part of the QB50 constellation.
• LituanicaSAT-2, a 3U CubeSat (4 kg) of Vilnius University, Lithuania. The CubeSat is part of the QB50 constellation with a FIPEX payload.
• NUDTSat (National University of Defense Technology Satellite), Belgium, a 2U CubeSat of NUDT for ionosphere research. NUDTSat features a FIPEX instrument of the QB50 constellation.
• Pegasus, a nanosatellite (2U CubeSat) of FH Wiener Neustadt, Austria (thermosphere research). Pegasus is a member of the QB50 constellation with the m-NLP payload.
• UCLSat (University College London Satellite), a 2U CubeSat of UCL with the INMS (Ion and Neutral Mass Spectrometer), ionosphere research. UCLSat is part of the QB50 constellation.
• URSA MAIOR (University of Rome la SApienza MicroAttitude In ORbit testing), a 3U CubeSat to study the lower thermosphere. USRA MAIOR is a member of the QB50 constellation with the m-NLP payload.
• VZLUSat-1, a 2U CubeSat Czech technology nanosatellite of VTLU, developed in cooperation with Czech companies (RITE, HVP Plasma, 5M, TTS, IST) and universities (CVUT, University of West Bohemia). The nanosatellite carries on board the following experiments: a miniaturized X-ray telescope, composite material for radiation shielding, FIPEX, a QB50 instrument, to measure the concentration of oxygen in the thermosphere.
Sensor complement: FIPEX [Φ-(Phi=Flux)-Probe-Experiment]
The FIPEX science unit consists of the following experiments: 5)
1) Φ-(Phi=Flux)-Probe-Experiment (FIPEX) is provided by the Institute of Aerospace Engineering of TU (Technische Universität) Dresden, Germany.
2) STM (Surface Thermal Monitor), supplied by MSSL (Mullard Space Science Laboratory) of Belgium.
FIPEX is able to distinguish and measure the time resolved behavior of atomic oxygen as a key parameter of the lower thermosphere. Atomic oxygen is the dominant species in these regions and therefore its measurement is crucial in the correlation and validation of atmosphere models. Moreover, erosion of spacecraft surfaces due to interaction with atomic oxygen is a serious concern and merits in-situ study in its own right.
The measurement is based on solid oxide electrolyte micro-sensors. For oxygen conducting solid state electrolytes, e.g. yttrium-doped zirconia, the conductivity starts at high temperatures and so the sensor operates at an elevated temperature of 600-700ºC, heated by an electrical resistance. Oxygen is "pumped" from one electrode to the other by an applied direct voltage and in accordance with Faraday's' law; the measured current is proportional to the mass flux by electrolysis.
The sensor needs to be in free flow and to determine the actual flux the attitude of the satellite with respect to its direction of motion needs to be known.
FIPEX on the ISS (International Space Station) was an experiment, launched on the STS-122 (1E) Shuttle flight on 7 February 2008 and deployed on the Columbus EPF (External Payload Facility) on the platform EuTEF (European Technology Exposure Facility). It provided the first measurements of the time resolved behavior of atomic oxygen and oxygen molecules. The next natural step would be a time and spatial resolved measurement, which is possible with QB50.
Figure 4: Photo of the FIPEX instrument on the QB50 precursor EM (Engineering Model) during development tests (image credit: TU Dresden)
The STM (Surface Thermal Monitor) experiment consists of six temperature transducers mounted as follows:
• Five channels are mounted on the CubeSat (on the inner side of solar panels)
• The sixth channel is mounted inside the FIPEX.
Figure 5: Connections of the STM; the sixth channel is not visible on connector (image credit: TU Dresden)
1) "LituanicaSAT-2," URL: http://n-avionics.com/projects/lituanicasat2-satellite-mission/
2) Information provided by Anerudha Mondal of the University of Vilnius, Lithuania
4) "Indian Launch Manifest of April 15, 2017," URL: http://www.sworld.com.au/steven/space/india-man.txt
5) "QB50 FIPEX Science Unit Interface Control Document," TU Dresden, document ILR-RFS_FPXQB50_ICD_1000_08, Issue 2.3, August 7, 2014, URL: https://www.qb50.eu/index.php/tech-docs/category/18-old-docs?download-62:fipex-icd-issue-2-3
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 (firstname.lastname@example.org).