Swarm Array Coherent Combining (SACC)

Smallsats offer significant potential in allowing for relatively inexpensive, rapid deployment and robust space operations, communications, science, etc. However, these smallsats are inherently power-limited and thus are correspondingly limited in their data rate capabilities. Accordingly, focus has been on constructing a swarm of these smallsats wherein each smallsat (or node) would transmit its individual signal that is then arrayed together to form a combined signal that has more power. The traditional approach to this arraying concept is to pre-condition each node signal in phase and time prior to transmission such that all signals arrive at the receiver coherently. This phase adjustment is very burdensome and problematic for the space node. We refer to this arraying approach as spaced-based arraying. Our innovation performs this signal arraying operation in a way that effectively eliminates all the node synchronization and coordination complexities noted above by implementing ground-based Arraying. We denote our innovative arraying technology as Swarm Array Coherent Combining (SACC). SACC uses ground terminal signal processing to extract node phasing and timing for coherent combining allowing each node signal to be uncoupled from each other and have significantly relaxed time and phase requirements. Also, noteworthy is that SACC technology provides the basis for a novel satellite relay concept that offers all the benefits of a large Phased Array in space by merely using a swarm of simple uncoupled smallsat transponder nodes that perform as elements of the array. Our SACC ground technology extracts all the phase information of these noise-dominated signals to achieve coherent node arraying. These space nodes do not need precise intra-swarm frequency and time coordination. Another key feature is that there is no need to calibrate any of the communication links even crosslinks. We refer to this novel relay system as the SACC SmallSat Relay System (SSRS). Smallsats offer significant potential in allowing for relatively inexpensive/robust space operations. However, these smallsats are power-limited which constrain their data rates. Focus has been on using a swarm of smallsats (or ‘nodes’) and to array/combine the node signals to form a high-power signal. The traditional approach is to pre-condition each node signal in phase/time so signals arrive at the receiver coherently. This approach is very burdensome for the space node and problematic to implement. Our innovation performs ‘arraying’ that eliminates all the node complexities noted above by using ground-based arraying. We denote our innovative arraying technology as “Swarm Array Coherent Combining” (SACC). SACC uses ground processing to extract phasing/timing for coherent combining while allowing nodes to be ‘uncoupled’ and have significantly relaxed requirements. SACC is the basis for a novel satellite relay concept (SACC SmallSat Relay System (SSRS)) that offers all the benefits of a large Phased Array in space by merely using a swarm of uncoupled smallsat transponder nodes. The overriding technical objective in Phase II are to prototype and field test the SSRS concept in order to upgrade our technology to a TRL 6. In this context, we have three technical objectives: Expand the MATLAB/Simulink modeling of Phase I Use our Firmware/Software Development and Test Laboratory to port the enhanced MATLAB/Simulink model to a System-On-a-Chip (SoC) architecture to allow RF to baseband processing at real time rates Conduct proof-of-concept testing and demos using UAVs as nodes in a UAV test range. Note that throughout these efforts, we will be using signals that reflect the ‘beyond-LEO’ signal characteristics that we had generated and first assessed in Phase I. Our MATLAB model expansion include key processing additions to include the multiple node channels and the Coherent Array combiner. In the second activity, we generate the code for the microprocessor and FPGA that will be hosted on a SoC. The output here are the digital components of the E2E system. A channel emulator will be used to add noise and Doppler during hardware-in-the-loop testing at Teltrium’s test facility. Lastly, we will conduct field testing using UAVs as nodes at a test range facility. The user transmitter, along with its signal emulators can be ground-based as would be the SACC GT processing. All testing results along with extensive TRL analyses will be provided as deliverables.

As NASA continues to explore our solar system, there is always a need for communications. With the vast emergence of smallsats both to do science and to support communications, the SACC SSRS represents a resilient, flexible and efficient way to leverage these smallsats to provide these NASA communications needs. In particular, because the SSRS imposes negligible requirements both on the swarm and its constituent transponder nodes, it can be easily designed and operationalized to support NASA communications over all space regimes. There is an ever-growing number of commercial smallsat constellations being deployed to support connectivity to the INTERNET. There are always issues related to achievable data rates and visibility to ground stations. Our SSRS offers the robust flexibility to create swarms of any size to address data rates. The SSRS also accommodates crosslinks between swarms with no impact on our SACC processing.

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