Next Generation Spacecraft Interconnect Standard (NGSIS)

Charles Patrick Collier AFRL/RVSV Kirtland AFB, NM

Introduction The realm of space is changing. We are, for the most part, all playing a role in the advancement of technologies that are altering how we gather data, how fast we gather that data, how we process that data, and how we transport that data within and out of the spacecraft. What we are tasked with, at this moment in time, is to re-discover together a plethora of existing methods by which we can alter the way we move information around a spacecraft.

Ever Changing Data Requirements Current and future spacecraft payloads and sensors generate data at volumes and rates that

exceed the capability of current spacecraft data handling architectures. These payloads and sensors include imaging systems, radar systems, signal collection systems, communications systems, and spacecraft health monitoring systems. In the past 5 years, we have seen the industry go from 1553 at 1Mbps to SpaceWire at 250Mbps to Time Triggered Gigabit Ethernet at 1Gbps. Over the next 5-10 years, requirements are expected to grow to 10Gbps to support high data rate instruments and onboard sensor data processing. New systems paradigms, including plug and play architectures and vehicle undoc/re-doc, will require extending interconnect capabilities and reliability levels well beyond those available in current technologies.

Future systems will implement higher-performance computer cores to accomplish on-board processing of raw data from the many sensors and sub-systems. Redundancy continues to be used to mitigate risk of component and sub-system failure, data transmission errors, and to increase the spacecraft mission life. The bandwidth capacity of the spacecraft bus data handling system must grow to accommodate increasing computer processing requirements, higher data rate sensors, and greater throughput requirements resulting from redundancy. Table 1, below, furthers this need for increased interconnect capabilities with examples of high data rate sensors that transmit Gbps worth of imaging information.

AVIRIS(1) CASI(2) HYDICE(3)

Image Resolution 614x512 578x578 320x420

Spectral Bands 224 288 210

Data Bandwidth (Gb/s) 25.4 34.6 5.8

Table 1: Legacy imaging systems that generate data streams in excess of 5Gbps. AVIRIS – Airborne Visible/Infrared Imaging Spectrometer

CASI – Compact Airborne Spectrographic Imager HYDICE – Hyperspectral Digital Imagery Collection Experiment

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The Next Generation Space Interconnect Standard

The NGSIS’s purpose is to evaluate and coalesce what may seem to be a varied number of requirements into a cogent list that is pervasive across agencies, and industry. These requirements cover physical interconnects within “boxes” and between “boxes”. Within the box, the standard will focus on chip-to-chip and board-to-board. These requirements also cover the method(s) by which we organize that data for transport, i.e. protocol suites. Low data rate, medium data rate, and high data rate ranges will also be explored within each of the three regimes listed above, i.e. chip-to-chip, board-to-board, and box-to-box. Consensus is driven by the needs and concerns of all participants. Use cases will help bound the problems by outlining general mission formats which will define how specific spacecraft communication bus architectures are created. The NGSIS is broken up into separate committees, each with a focused area. These are shown in Figure 1 below.

Figure 1: Organizational Chart of the NGSIS

Conclusion It is not expected that at the end of it all, the NGSIS will publish a solution that fits all the problems presented. It is more likely that we have before us a small set of answers that scale with the problem presented. This applies to a physical interconnect where we will see photonic links given a certain met threshold, e.g. data rate; otherwise, we will apply a standard copper bus. This also applies to the type of protocol suite selected to control the flow of data throughout the spacecraft; whether it is on a high data rate section of the network, or on a low data rate portion that is concerned with health, guidance, and navigation.

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