John R. Dickinson

CYGNSS: Enabling the Future of Hurricane Prediction [Remote Sensing Satellites]

The CYGNSS mission introduces a new paradigm in low-cost Earth science missions that employs a constellation of science-based microsats to fill a gap in capabilities of existing large systems at a fraction of the cost. The CYGNSS observatories will make frequent wind observations, and wind observations in precipitating conditions, using GPS reflectometry to observe the TC inner core ocean surface. These efforts will result in unprecedented coverage of windswithin a TC throughout its life cycle and thus provide critical data necessary for advancing the forecast of TC intensification.

The CubeSat Heliospheric Imaging Experiment (CHIME)

We describe a CubeSat mission to predict and diagnose space weather events at Earth by tracking the interplanetary disturbances that cause those effects. Our demonstration mission, the CubeSat Heliospheric Imaging Experiment (CHIME), is a wide-field sky camera that can image large, tenuous clouds of material as they cross the inner solar system en-route to Earth. These clouds, known as interplanetary coronal mass ejections (ICMEs), are produced by magnetic activity at the Sun, and consist of billions of tons of magnetized plasma that streak across the solar system at incredibly high velocities, upwards of 8 million km/hour. Impact of ICMEs on the Earths magnetosphere cause geomagnetic storms at earth, a type of space weather event. Major space weather events cause magnetic storms, aurora, ionospheric radio interference, and intermittent satellite radiation exposure. ICME tracking requires modest resolution and data rates, and is well suited to the CubeSat platform. CHIME will enable ongoing developmental space weather prediction, demonstrate the heliospheric imaging concept on the Cube- Sat platform, and advance the state of CubeSat readiness for many applications. Further, CHIME is a stepping stone to an agile, operational space weather imaging system, using moderate numbers of extremely inexpensive, redundant spacecraft to achieve robust operational reliability from commercial grade parts.

Avionics of the Cyclone Global Navigation Satellite System (CYGNSS) microsat constellation

The Cyclone Global Navigation Satellite System (CYGNSS), which was recently selected as the Earth Venture-2 investigation by NASAs Earth Science System Pathfinder (ESSP) Program, measures the ocean surface wind field with unprecedented temporal resolution and spatial coverage, under all precipitating conditions, and over the full dynamic range of wind speeds experienced in a tropical cyclone (TC). The CYGNSS flight segment consists of 8 microsatellite-class observatories, which represent SwRIs first spacecraft bus design, installed on a Deployment Module for launch. They are identical in design but provide their own individual contribution to the CYGNSS science data set. Subsystems include the Attitude Determination and Control System (ADCS), the Communication and Data Subsystem (CDS), the Electrical Power Supply (EPS), and the Structure, Mechanisms, and Thermal Subsystem (SMT). This paper will present an overview of the mission and the avionics, including the ADCS, CDS, and EPS, in detail. Specifically, we will detail how off-the-shelf components can be utilized to do ADCS and will highlight how SwRIs existing avionics solutions will be adapted to meet the requirements and cost constraints of microsat applications. Avionics electronics provided by SwRI include a command and data handling computer, a transceiver radio, a low voltage power supply (LVPS), and a peak power tracker (PPT).

CYGNSS command and data subsystem and electrical power subsystem phase A and B developments

The Cyclone Global Navigation Satellite System (CYGNSS), which was selected as the Earth Venture-2 investigation by NASAs Earth Science System Pathfinder (ESSP) Program, measures the ocean surface wind field with unprecedented temporal resolution and spatial coverage, under all precipitating conditions, and over the full dynamic range of wind speeds experienced in a tropical cyclone (TC). The CYGNSS flight segment consists of 8 microsatellite-class observatories, which represent SwRIs first spacecraft bus design, installed on a Deployment Module for launch. The microsatellites (microsats) are identical in design but provide their own individual contribution to the CYGNSS science data set. Within the first year of the CYGNSS program (Phase A and B), the design has been analyzed, vetted, and reviewed which culminated in a succession of updates and design improvements. This paper will discuss relevant updates to the electrical systems of the microsat, specifically the command and data subsystem (CDS) and the electrical power subsystem (EPS). For the CDS, more detailed analysis of the communication link and maturation of the transceiver module design are presented. The link budget was reviewed by the team and verified via simulation. The transceiver module has moved to a dedicated box consisting of a radio frequency (RF) board and a digital signal processing (DSP) board. For the EPS, a detailed power analysis of the mission has led to an update in the solar array configuration. The details of the power analysis, which is performed in STK and Matlab, are presented.

CubeSats to NanoSats; Bridging the gap between educational tools and science workhorses

Since their initial development and launch in the early 2000s, the CubeSat platform has captured the imagination and energy of our next generation of spacecraft technologists around the world. Once thought of by the established space community as “toys” and educational novelties, the CubeSat has revolutionized the space-community and broken the acceptance barrier with proven development and on-orbit performance. Leveraging CalPolys published specification, CubeSats have demonstrated the advantages of a common form factor that can be launched and deployed using a common deployment system by smashing the cost-to-orbit price-point while offering significant mission manifest flexibility. The challenge now lies in transitioning the strengths and success of the CubeSat to mainstream science investigations. While the CubeSats successes combined with todays budget constraints have served to open the established space community to discussions of innovative ideas to reduce costs; it faces both perceived and real constraints related to mission applications, reliability, payload performance, communications, and operations. The CubeSat model must be evolved to penetrate the stigmas and applied appropriately to become an accepted tool in the world of mainstream science investigations. This paper identifies issues and presents potential solutions and lessons-learned regarding these issues based on several recent mission concept developments for potential real-world applications.

Towards a practical cognitive communication network for satellite systems

We present progress toward the formulation of a mathematical model for a cognitive communication network with applications to satellite systems. Our model employs abstract concepts including communicators, communications channels, and demand for capacity. These model elements may be tailored to represent a wide variety of practical communication scenarios. We present a dynamic automated reasoning methodology which uses the model to find communication resource allocations for specific scenarios that are superior to static scheduling approaches. This reasoning process resolves resource dependencies, enforces communication policies, and learns from previous communication attempts. We have implemented this reasoning process using Answer Set Prolog and used it to plan communications for a constellation of 8 satellites and 3 ground stations. The example demonstrates performance improvement over a static scheduling approach and shows how solutions can be found with reasonable computational effort.

A reconfigurable, radiation tolerant S-Band radio for space use

Southwest Research Institute (SwRI) is developing a reconfigurable, radiation tolerant, communication system that addresses the needs for low-cost, quick turn spacecraft, as well as the reliability and connectivity required in harsh radiation environments of higher orbit systems. The core of such a Flexible Communication Platform (FCP) centers on a Software Defined Radio (SDR) architecture providing S-Band (2 GHz) communications. The Digital Processing Unit (DPU) fits in a 1U form factor and forms half of a two-slice approach (RF front-end is on a separate slice). The architecture of the DPU is based on the Virtex-4, an SRAM-based FPGA from Xilinx. SRAM-based FPGAs, however, have significant limitations in spacecraft systems due to radiation susceptibility of the FPGA programming cells. SwRI chose to implement a combination of triplicated logic (TMR) and Configuration Memory Scrubbing, specifically in an external RAD-Hard device, to mitigate radiation effects on the system. The flexible design of the DPU allows rapid integration into multiple target mission architectures. When coupled with the RF front-end, the FCP is capable of communicating from LEO and MEO orbits using a variety of wideband signals and protocols.

A high-density, non-volatile mass-memory and data formatting solution for space applications

The Instrument Storage Module was designed to provide a single-board path from a satellites instruments to its transmitter. It is equipped with custom interfaces to the instrument, CCSDS formatting algorithms implemented in an FPGA, mass-memory storage, and a direct X-Band or Ku-Band transmitter output interface. In order to pinpoint and eliminate any bottlenecks in maintaining a continuous 150 Mbps downlink rate, we have studied the bandwidth of individual component blocks in the data flow and present the results in this article. Our analysis consists of FPGA simulation, FPGA timing design, and board layout timing analysis. The results indicate that the output to the transmitter is capable of continuous downlink of up to 168 Mbps (Section 3), providing 12% margin over the downlink requirement (limited primarily by the serializing algorithms in the FPGA).1,2

The high reliability southwest LEO Explorer (SLX-6) CubeSat bus

Southwest Research Institute (SwRI) has developed the Southwest LEO EXplorer (SLX-6), a standard 6U CubeSat in a 2U × 3U form factor intended to carry a payload into a variety of Low Earth Orbits. SLX-6 also serves as the basis for the Southwest Deep-Space Explorer (SDX-6) that SwRI is developing for the CubeSat mission to study Solar Particles (CuSP) mission (Figure 2). The SLX-6 is built to a tailored NPR-7120 approach adapted from SwRIs experience in Class B, C, and D missions. Program execution will include bus component selection, testing, and analysis; mechanical design and analysis (structural and thermal); bus and Attitude Determination and Control Subsystem (ADCS) flight software (FSW) definition and tailoring; bus Electrical Ground Support Equipment (which transitions into the ground data system); Assembly Integration and Testing (AI&T) including Thermal Vacuum (TVAC), Vibration (Vibe), Shock (as needed), and EMI/EMC environmental testing; and NASA operations support. The SLX-6 is novel in three distinct ways when compared to other off-the-shelf CubeSat solutions: the SLX-6 is a high reliability bus; it is robust to all space environments, including radiation; and SwRI offers a one-stop-shop for all portions of a satellite mission. The SLX-6 is designed with a robust parts program that is derived and tailored from EEE-INST-002 to be cost competitive. This same parts program is invoked when selecting radiation tolerant components. Analysis is performed in-house to ensure that the mechanical design of the observatory is compatible with environments in GEVS (GSFC-STDF-7000A). SwRI has extensive experience with all portions of satellite design and test: electrical analysis, design, and test; mechanical analysis, design, and test; flight software analysis, design, and test; component- and bus-level integration, testing, and qualification. SwRI is also presently evaluating quotes a 13meter multi-band ground station on campus. This paper will address the CubeSat description, subsystems, analysis and testing philosophies, and integration and testing approach.