All 2011 content

Lessons from 5 Years of Space Plug & Play Avionics (SPA) Device Development with High School Students

Paul Jaffe et al. — Thu, 11 Aug 2011 14:29:00 PDT

One approach to reduce spacecraft development time and cost is the use of Space Plug & Play Avionics (SPA). Initially introduced in 2004, SPA offers standardized power and data interfaces to allow for rapid design, integration, and testing of spacecraft. SPA endeavors to leverage, where possible, existing standards and tools to help maximize the potential user base without requiring specialized or new knowledge. Some examples include USB and SpaceWire for hardware interfaces, and C and FPGA constructs for software and firmware. In many high schools, emphasis on technology education has meant that students may have already been exposed to these concepts and techniques. Additionally, many motivated students have extensive backgrounds in software and hardware development outside of academic venues. The Naval Research Laboratory (NRL) is one of many organizations that participate in internship programs designed to introduce students to real science and engineering environments. We have used these opportunities for students as a pedagogical vehicle for SPA device development. From 2006 to 2010, we learned a number of lessons that may be of interest to SPA developers and technology educators.

CubeSat Components: A Collection of Ideas from AFRL Space & Phillips Scholars

Keith Avery et al. — Thu, 11 Aug 2011 14:14:00 PDT

CubeSats are fast becoming recognized as key elements of a satellite portfolio. Industry, academia, and government agencies are all participating in the development of these micro-satellite platforms for use as operational systems, testbeds, or as learning tools for young engineers. The Air Force Research Laboratory (AFRL) Space Electronics Branch (RVSE) participates in the AFRL Space Scholar and Phillips Scholar programs which promotes mentoring young engineering students by AFRL/RVSE staff. As part of this program RVSE provides ideas for projects that the students will work on during their summer at the laboratory. This idea list includes the development of components that could be used for CubeSats and can range from the structure itself to individual modules that can be used across multiple missions. The primary goal was to provide solid engineering experience using real-world examples with useable hardware or designs as the output. This would give the students a quick emersion into the engineering process complete with reviews and documentation. A group of eighteen students ranging from juniors in high school to graduate students in engineering were assembled. The group developed several ideas that can be used for future CubeSat missions. In this paper we will describe a subset of the overall group of ideas.

Aeneas -- Colony I Meets Three-Axis Pointing

Michael Aherne et al. — Thu, 11 Aug 2011 13:59:00 PDT

A dedicated satellite mission is currently under development at the USC Space Engineering Research Center. Named “Aeneas,” (after the Trojan warrior who personifies duty and courage) the cubesat will be used to track cargo containers worldwide. To accomplish this feat, the satellite must maintain a 2-degree-accuracy surface track – the first of its kind in cubesat technology. This paper describes the requirements, design, implementation and tests to date in the areas of: flight dynamics, flight software, deployable spacecraft antenna, store-and-forward software, custom flight processor including MEMS gyroscopes, Doppler-based orbit determination enhancement and mobile ground station dish with helical feedhorn. Details are provided about the attitude control system and communications.

Dynamic Ionosphere Cubesat Experiment (DICE)

Geoff Crowley et al. — Thu, 11 Aug 2011 13:45:00 PDT

The Dynamic Ionosphere Cubesat Experiment (DICE) mission is due to launch in October 2011 on a NASA rocket from Vandenburg Air Force Base. DICE was selected for flight under the NSF "CubeSat-based Science Mission for Space Weather and Atmospheric Research" program. Space weather refers to conditions in space (the Sun, solar wind, magnetosphere, ionosphere, or thermosphere) that can influence the performance and reliability of space-borne and ground-based technological systems. Ionospheric variability has a particularly dramatic effect on radio frequency (RF) systems; for example, large gradients in ionospheric electron density can impact communications, surveillance and navigation systems. Some of the largest gradients are found on the edges of Storm Enhanced Density (SED) features, which regularly occur over the US in the afternoon during magnetic disturbances. The DICE mission has three scientific objectives: (1) Investigate the physical processes responsible for formation of the midlatitude ionospheric Storm Enhanced Density (SED) bulge in the noon to post-noon sector during magnetic storms; (2) Investigate the physical processes responsible for the formation of the SED plume at the base of the SED bulge and the transport of the high density SED plume into the polar cap; (3) Investigate the relationship between penetration electric fields and the formation and evolution of SED. The mission consists of two identical Cubesats launched simultaneously into a near circular 600 km, nearly sun-synchronous orbit in the evening sector, precessing to earlier local times. Each satellite carries a fixed-bias DC Langmuir Probe (DCP) to measure in-situ ionospheric plasma densities, and an Electric Field Probe (EFP) to measure DC and AC electric fields. Additionally, a science-grade magnetometer will measure field-aligned currents. These measurements will permit accurate identification of storm-time features such as the SED bulge and plume, together with simultaneous co-located electric field measurements, which have previously been missing. The mission team combines expertise from ASTRA, Utah State University/Space Dynamics Laboratory (USU/SDL), Embry-Riddle Aeronautical University and Clemson University. A large number of students (too many to list) have been involved in building and testing the DICE spacecraft, and this is truly a student experiment.

PEZ: Expanding CubeSat Capabilities through Innovative Mechanism Design

Tyler Murphy et al. — Thu, 11 Aug 2011 13:30:00 PDT

Since the beginning of the CubeSat program, developers have been pushing the envelope of the capabilities that can be achieved in such a small and standardized package. As CubeSat missions have become more complicated the external surface area of these cubes has become a limiting factor for the missions. In order to harvest as much power as possible, the external surfaces are usually dedicated solely to solar arrays, thus limiting the external surface area that can be used for the primary mission. The ALL-STAR mechanical team has developed an innovative and unique system that allows for both the electrical power subsystem engineer and the science instrument engineer to have full access to the exterior of the satellite without sacrificing any of the quality or capabilities of the CubeSat and its overall mission. In order to accomplish this, the ALL-STAR team has developed mechanisms that deploy both solar arrays and the payload section from the standard 3U CubeSat. The PEZ (Payload Extension Zone) effectively doubles the available area for the solar array on the CubeSat as well as allowing the payload to have access to the exterior of the satellite. These mechanisms are also innovative in that they use simple concepts and mechanisms to greatly reduce their impact on the mass and volume of the CubeSat as a whole. Through this cooperative design between maximum power collection and payload access, the ALL-STAR bus will allow for even greater CubeSat capabilities to be achieved.

The ExoplanetSat Mission to Detect Transiting Exoplanets with a CubeSat Space Telescope

Matthew Smith et al. — Thu, 11 Aug 2011 13:15:00 PDT

We present a CubeSat mission for the discovery of exoplanets down to 1 Earth radius around the nearest and brightest Sun-like stars. The spacecraft prototype―termed ExoplanetSat―is a 3U space telescope designed to monitor a single target from low Earth orbit. The optical payload will precisely measure stellar brightness, seeking the characteristic dip in intensity that indicates a transiting exoplanet. Once ExoplanetSat identifies a candidate exoplanet, larger assets can be used to conduct follow-up observations to characterize the atmospheric constituents. The prototype will serve as the basis of an eventual fleet of nanosatellites, each independently monitoring a single bright, nearby star. Given the spacecraft’s low mass and sub-pixel sensitivity variations in the science detector, image jitter and its resultant photometric noise is a primary concern. The attitude determination and control subsystem (ADCS) mitigates this using a two-stage pointing control architecture that combines 3-axis reaction wheels for arcminute-level coarse pointing with a piezoelectric translation stage at the focal plane for fine image stabilization to the arcsecond level. The ExoplanetSat optical design combines star camera and science functions into a single device that fits into the 3U form factor. This paper presents the ExoplanetSat science case, mission overview, concept of operations, and spacecraft configuration.

Characterization and Analysis for Flying COTS Electronics On-Orbit

Jason Niederhauser et al. — Thu, 11 Aug 2011 13:00:00 PDT

As part of the Air Force Institute of Technology's efforts to develop and fly a novel imaging chromotomographic spectrometer payload in space, this work accomplished an investigation of hermetic enclosures to house commercial, off-the-shelf (COTS) components. Rationale for expending research efforts herein is attributable to enabling use of electronics which may not be available in a space-qualified form for years and to reduce cost/schedule constraints. Thermal modeling was validated through performance of a design, analysis and test campaign.

RockOn and RockSat: A NASA and COSGC Collaboration to Train Tomorrow's Engineers

Chris Koehler et al. — Thu, 11 Aug 2011 12:45:00 PDT

Colorado Space Grant Consortium's (COSGC) newest sounding rocket payload program, RocketSat, has been in development since 2005. By 2008, COSGC had developed a body of knowledge on building sounding rocket payloads that had reached a level it was ready to pass on to other students across the nation. Taking the lessons learned from three years of experience and three suborbital flights, COSGC faculty and students developed a standard payload to characterize the flight environment and measure radiation on the flight trajectory. The construction of this standard payload was turned into the RockOn workshop through a partnership with NASA’s Wallops Flight Facility (WFF), NASA Education, the Colorado and Virginia Space Grant consortia. Over the course of the 6-day, hands-on RockOn workshop, university students and faculty build and test a fully functional sounding rocket payload and watch their payloads launch on a Terrier-Improved Orion to an altitude of approximately 70 miles. The payloads are then recovered, and participants analyze their flight data. The first RockOn launch was June 25, 2008, and since then two more workshop and launches have occurred in 2009 and 2010, with another scheduled in 2011. In an effort to continue this learning process, the canisters (RockSat Payload Canisters) used to streamline integration of the RockOn payloads are offered to universities at a fraction of the cost of the launch vehicle costs. This provides students across the United States with a standard interface and relatively inexpensive flight opportunity once a year to launch their payloads, building on the initial knowledge gained from the RockOn workshop. This student-managed national program organized at COSGC is known as RockSat and has flown 21 payloads from 11 universities on three sounding rocket flights in 2008, 2009, and 2010, with another 9 payloads scheduled to launch in 2011. The goal of RockSat is to foster the continued learning about the process of engineering and design after the RockOn Workshop with an original payload, as opposed to a predesigned payload. In 2010, WFF and COSGC began developing the RockSat-X program. Like RockSat, RockSat-X is a national, student-managed program. The biggest difference between RockSat and RockSat-X is that the latter provides full access to the space environment, power and telemetry, and the possibility to eject sub payloads. The first launch of RockSat-X is in July 2011. Students that partake in the RockOn Workshop and/or RockSat-C and X programs gain a level of hands-on learning unlike anything the classroom can provide. In addition to providing invaluable training with physical payloads, these programs have proven to be an excellent test bed for small satellite technology as student teams take off with original mission ideas. The next step is to further develop RockSat-C and RockSat-X payloads into small student satellites intended for orbit and create a program, through partnerships with WFF and others, to launch them on a consistent basis.

Real Science, Real Education: The University Nanosat Program

David Voss et al. — Thu, 11 Aug 2011 12:30:00 PDT

The University Nanosat Program (UNP) is a two year small satellite competition held among leading universities across the nation. In the past 12 years, UNP has involved 27 universities and over 5000 students in a variety of engineering fields and other disciplines, in the process of designing and managing the development of a satellite. The UNP is a partnership between the Air Force Office of Scientific Research (AFOSR), the Air Force Research Laboratory (AFRL), and the American Institute of Aeronautics and Astronautics (AIAA). The program’s primary purpose is to help train engineering students in satellite design, fabrication, and testing by requiring them to build the satellite themselves through the mentorship of their Principle Investigator, industry mentors, and a series of six program reviews managed by the AFRL Program Office. Each university-built satellite attempts to further a specific technology or perform a scientific mission. Technologies advanced through the program include all aspects of small satellite designs including structures, propulsion, imaging, and navigation and have helped further science payloads such as energetic particle detectors, plasma probes, photometers, and many others. This paper will discuss the educational impact on students involved in a hands-on, hardware focused program. The paper will also address the recent launch of FASTRAC, the Nanosat-3 (NS-3) competition cycle winner built by the University of Texas at Austin, the upcoming launch of CUSAT, the NS-4 winner built by Cornell University; as well as the NS-5 winner DANDE built by the University of Colorado - Boulder. It will discuss the program’s design philosophy as well as the challenges in creating space flight hardware with a small budget on a student schedule. Finally, the article will discuss some of the upcoming changes in the program such as the acceptance of CubeSats as equal competitors with the standard 50 kg nanosatellites.

GNSS Receive Antennas on Satellites for Precision Orbit Determination

Jan Zackrisson et al. — Thu, 11 Aug 2011 11:29:00 PDT

This paper presents GNSS (Global Navigation Satellite System) antennas developed for different earth observation missions. Such missions often require Precise Orbit Determination (POD). The largest error contribution to POD measurements is usually local multipath, i.e. signals reflected in the satellite structure. Antenna radiation in the back direction must hence be suppressed, while at the same time keep a good coverage at low elevation angles. This is normally achieved by using a standard antenna element placed in a larger choke ring structure. The disadvantage with this arrangement is that the antenna becomes large and relatively heavy. The objective has hence been to develop small and lightweight antennas with low back radiation in combination with good coverage. We have worked with both low profile Patch Excited Cup (PEC), as well as helix antennas. Two of the described antennas are PEC antennas. One smaller, suitable on satellites without large flat mounting areas, and one design where the low elevation gain was traded against the back radiation and a good compromise was achieved using only two narrow choke rings to facilitate mounting on larger flat surfaces. A high-performance conical quadrifilar helix antenna has earlier been developed for applications where a taller antenna can be accommodated.