Research in the field of Nano Satellites covers several areas, ranging from avionics design, sensors to the design of specific applications and missions. Without claiming to be exhaustive, given the vastness and interdisciplinarity of the topics, it is possible to provide a rough outline of the research and development areas related to the design of a satellite mission based on mini-satellite and nano-satellite technologies. Starting from the lowest level, the research topics are related to the design of the satellite vector (avionics and communications) and payload (sensors of different types) while at a higher level the research focuses on signal processing and on-board processing techniques to optimize the various phases of information acquisition and data production. More advanced research themes concern both the use of data provided by signal and on-board processing technologies and their integration with other information sources to solve more complex problems.
In the field of telecommunications, moreover, CubeSat Nanosatellites with a payload capacity to transmit data are at an advanced stage of development.
For the first 10 years of research (from 1999 to 2009) the sectors involved were those of education and the payload only had to perform very simple operations such as:
Several missions have been developed subsequently but only during the last five years has there been an increase in these studies, linked to different types of application and test missions ranging from monitoring applications to telecommunications applications. For these various missions, different payload technologies have been used for data transmission and operating in different Radio Frequency bands.
These types of studies have led to a fairly consolidated scenario in which CubeSat technology is used in the telecommunications sector with CubeSat constellations of satellites operating in Low Earth Orbit (LEO Low Earth Orbit) to support the existing infrastructure on Earth to perform functions such as:
Another important application developed from the research conducted on payloads and communication protocols within the CubeSat was the Mar-CO Mars Communication Observation mission (implemented with 6U CubeSat technology) which contributed to the communication functions between Earth, the InSight spacecraft and the Rover, in its mission to Mars. The technology used has allowed to address the problems of end-to-end connection discontinuity and has experimented with new architectures with DTN (Delay Tolerant Network) communication protocols.
The use of CubeSat technology and payload and communications protocols in a context such as that of a space mission opens up possible future scenarios in which these technologies could be used to guarantee a telecommunications infrastructure for space communications between Earth and missions in the Solar System. These hypotheses could serve as a leverage for new research work to achieve requirements that are not yet feasible. In fact, a necessary increase in the 9600 kbps data rate to Gpbs data rates is hypothesized, as well as a high degree of flexibility characterized by the possibility of establishing Inter Satellite Links (ISL) and connections with different reception stations (operating in very different conditions).
Finally, a greater communication capacity of the satellites at constellation level will be required, possibly integrating 5G architectures with DTN protocols. Part of these requirements, as we will see, are already addressed in research topics. In particular, payloads related to communication in recent years have undergone a considerable technological evolution, moving from the first systems operating in UHF/VHF bands with data rates of 9600 bps, to systems operating in the S band (for Telemetry at 2 GHz) and X band (7-8 GHz), such as those used in RAX and GOMX-3 missions, with data rates of up to 1 Mbps, and reaching the most recently developed technology for Nanosatellites, with Reflector and Reflector array type antennas, in the bands (12-14 GHz) , K (18 GHz) and Ka (20-30 GHz) and with data rates of up to 100 Mbps. Further studies are evolving or may evolve towards the use of other frequencies with the Q band (33-50 GHz) and the V band (50-75 GHz) which have been positively evaluated to implement intrasatellite ISL connections (also between satellites in different orbits, such as GEO (Geostationary Orbit 36).000 Km), MEO (Medium Orbit between 3,000 and 12,000 Km) and LEO (Orbit between 400 and 1,200 Km) or for downlinks from Very Low Earth Orbits (VLEO up to 150 Km). For example, V-band technology has been used in the Starlink project with VLEO units in orbit. The W-band (75-110 GHz) could also be used, as demonstrated by the recent ESA W-Cube project, consisting of a CubeSat with a W-band transmitter used for propagation measurements at those wavelengths. Further studies are focusing on the possibilities of using optical wavelength communications also on Nanosatellites.
This approach would guarantee high data rates, up to 10 Gbps but with consumption in the order of 50W and an evolutionary trend is not yet evident. In any case, tests have already been developed for inter-satellite ISL communication and for study purposes also with “optical” ground receiving stations. The latter, however, are limited to operating in the absence of weather clouds, so hybrid developments of the RF/Optical type are foreseeable (for example, alongside optical transmitters with systems operating in the X-band). A further emerging technology, which will allow different application advantages, is that of Payload Software Defined Radio (SDR).
Some examples of application on large satellites have demonstrated the effectiveness of SDR technology and the use in systems based on Nanosatellites is not precluded by particular limitations. In particular, the adoption of SDR payloads would allow the optimal exploitation of resources, allowing rapid adaptation to the mission requirements for telecommunications. In fact, the programmability of these systems enables the support of multiple signals, the increase in data rate on reliable channels and the optimization of the electromagnetic spectrum for telecommunications. Few SDR payloads have already been used in small satellites and others are under development, such as AstroSDR, NanoDock SDR, GAMALINK and STI-PRX-01. The use of this technology may lead to future developments for the implementation of the Software Defined Networking concept, i.e. highly configurable networks consisting of different types of links between various satellites and ground stations. In such a scenario, the introduction of Cube Sat constellations will enable the implementation of increasingly performing and configurable ISL inter-satellite links, for example with connections between GEO, MEO, LEO (or HAPS) satellites and ground stations.
The ARAMIS project developed by Italspazio aims at the study, design and future implementation and verification of advanced space technologies for CubeSat, and the creation of a Low-Cost satellite constellation based on CubeSat (12U nanosatellites) communicating with each other via ISL LEO-LEO in the Q-band and capable of cooperating with the geostationary satellite Athena-Fidus via high-capacity Ka-band ISL. The ARAMIS Project is a flexible and cost-effective response to increase the transmission capacity of CubeSat and complementary satellites and/or enhance services already offered by other space segments through its cooperative use and ensuring total accessibility and exclusivity of services and increased availability of the service in the regions of interest. ARAMIS foresees different types of applications/payloads:
The system is characterized by the following sub-assemblies:
Particular attention is paid to the development of the SDR Modem, which will be realized in SDR-FPGA technology. Open-Source libraries will be used for frequency, phase and symbol synchronism recovery algorithms. The VHDL language will be used for the FPGA development phase. The choice of HW FPGA will be made among the available COTS products.
The ARAMIS Situational Awareness ARAMIS payload could be based on a very flexible SDR design able to meet current standards operating in the UHF bandwidth (400-3000 MHz). In particular, LoRa-E is specifically focused for its ability to operate with very low SNR (Signal to Noise Ratio), allowing long resilience, low detectability and low power consumption of the ground terminal batteries. A deployable UHF antenna with 6 dBi gain will collect the ground data, while the implementation of an S-band transmitter can be a good option to control the ground terminals. The collected data will be stored in the CubeSat mass memory to be sent via ISL to the ground station after formatting and encryption.
For ELINT applications, the activity consists in receiving data related to transmission sources, in particular the emissions of the various types of radar. The interceptions can be carried out by ELINT stations located on the ground near the borders of the opponent, on specifically equipped ships and/or aircraft or on artificial satellites (CubeSat – ARAMIS). The ELINT application payload, operating according to a TDOA/FDOA approach, is based on a formation of three satellites each with a large BW signal acquisition payload and includes two large BW deployable antennas, followed by innovative receiver chains. The formation configuration includes two satellites on the same orbital plane and a third in flight. Relative positions are calculated by processing the powerful EGNSS receivers. Data transformation and the location and analysis of the ground source are performed on the ground in the processing center.
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