Systems engineering of inter-satellite communications for distributed systems of small satellites

2015 ◽  
Author(s):  
W. Edmonson ◽  
S. Gebreyohannes ◽  
A. Dillion ◽  
R. Radhakrishnan ◽  
J. Chenou ◽  
...  
Keyword(s):  
Distributed Systems ◽  
Systems Engineering ◽  
Satellite Communications ◽  
Small Satellites

scholarly journals Remote sensing of aerosols with small satellites in formation flight

2018 ◽  
Vol 11 (7) ◽  
pp. 3935-3954 ◽  
Author(s):  
Kirk Knobelspiesse ◽  
Sreeja Nag
Keyword(s):  
Remote Sensing ◽  
Optical Properties ◽  
Information Content ◽  
Systems Engineering ◽  
Limited Information ◽  
Aerosol Optical Properties ◽  
Small Satellites ◽  
Analysis Technique ◽  
Technological Developments ◽  
Aerosol Remote Sensing

Abstract. Determination of aerosol optical properties with orbital passive remote sensing is a difficult task, as observations often have limited information. Multi-angle instruments, such as the Multi-angle Imaging SpectroRadiometer (MISR) and the POlarization and Directionality of the Earth's Reflectances (POLDER), seek to address this by making information-rich multi-angle observations that can be used to better retrieve aerosol optical properties. The paradigm for such instruments is that each angle view is made from one platform, with, for example, a gimballed sensor or multiple fixed view angle sensors. This restricts the observing geometry to a plane within the scene bidirectional reflectance distribution function (BRDF) observed at the top of the atmosphere (TOA). New technological developments, however, support sensors on small satellites flying in formation, which could be a beneficial alternative. Such sensors may have only one viewing direction each, but the agility of small satellites allows one to control this direction and change it over time. When such agile satellites are flown in formation and their sensors pointed to the same location at approximately the same time, they could sample a distributed set of geometries within the scene BRDF. In other words, observations from multiple satellites can take a variety of view zenith and azimuth angles and are not restricted to one azimuth plane as is the case with a single multi-angle instrument. It is not known, however, whether this is as potentially capable as a multi-angle platform for the purposes of aerosol remote sensing. Using a systems engineering tool coupled with an information content analysis technique, we investigate the feasibility of such an approach for the remote sensing of aerosols. These tools test the mean results of all geometries encountered in an orbit. We find that small satellites in formation are equally capable as multi-angle platforms for aerosol remote sensing, as long as their calibration accuracies and measurement uncertainties are equivalent. As long as the viewing geometries are dispersed throughout the BRDF, it appears the quantity of view angles determines the information content of the observations, not the specific observation geometry. Given the smoothly varying nature of BRDF's observed at the TOA, this is reasonable and supports the viability of aerosol remote sensing with small satellites flying in formation. The incremental improvement in information content that we found with number of view angles also supports the concept of a resilient mission comprised of multiple satellites that are continuously replaced as they age or fail.

DESIGN, IMPLEMENTATION AND TESTING OF A FLEXIBLE FULLY-DIGITAL TRANSPONDER FOR LOW-EARTH ORBIT SATELLITE COMMUNICATIONS

2014 ◽  
Vol 23 (10) ◽  
pp. 1450148 ◽  
Author(s):  
DANIELE DAVALLE ◽  
RICCARDO CASSETTARI ◽  
SERGIO SAPONARA ◽  
LUCA FANUCCI ◽  
LUCA CUCCHI ◽  
...  
Keyword(s):  
Power Consumption ◽  
Satellite Communications ◽  
Intermediate Frequency ◽  
Scientific Data ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Hardware Complexity ◽  
Digital Radio ◽  
Small Satellites ◽  
Control Configuration

This paper presents a flexible Telemetry, Tracking & Command (TT&C) transponder for Earth Observation (EO) small satellites. The proposed device adds to the state-of-the-art EO TT&C transponders the possibility of scientific data transfer thanks to the high downlink data-rate (up to 40 Mbps) and in-flight reconfigurability via Telecomand (TC). The integration of these features in one single device represents a considerable optimization in terms of mass budget, which is important for EO small satellites. Furthermore, in-flight reconfigurability of communication parameters via TC is important for in-orbit link optimization, which is especially useful for Low-Earth Orbit (LEO) satellites where visibility can be as short as few hundreds of seconds. The proposed transponder is a digital radio unit working at 70 MHz intermediate frequency (IF). A new custom and configurable hardware accelerator was developed to cover intensive radio DSP functions at IF. The custom hardware is integrated in a single FPGA with a space-compliant processor core, for control, configuration and interface with the other satellite subsystems. All the quantization parameters were fine-tailored to reach a trade-off between hardware complexity and implementation loss (IL). The IF RX/TX ports require eight bits and seven bits, respectively. The IL is 0.5 dB at BER = 10-5 for the RX chain. A system proof-of-concept was implemented on the Xilinx Virtex 6 VLX75T-FF484 FPGA. The total device occupation is 82%. The power consumption of the design fitted in FPGA is less than 2 W. The power consumption of the whole demonstrator board is less than 9 W.

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