Small and Increasingly Capable

Written by Scott MacGillivray

• the worldwide development of low-power miniature electronics;
  
• the growing use by organizations (e.g., industry, academia and emerging space-faring countries) to build nanosatellites; and
  
• shrinking budgets, forcing projects to be done with less money.

Analogous to the personal computer market in the early 1980s when their utility was constrained by lack of performance, the steady march of technology development will grow small satellite capabilities to perform increasingly more capable missions. Today, the missions most discussed for smaller satellites such as microsatellites (less than 100 kilograms, or 220 pounds) and nanosatellites (less than 10 kg) are as low-cost on-orbit test beds for performing space weather and environmental science. Though, quickly fielded technology currently being matured are missions that utilize small constellations in low Earth orbit to provide persistent 24/7 data-gathering using advanced optics or deployable high-gain antennas. While they will never replace the need for larger spacecraft where high power and large aperture are vital, the use of miniature spacecraft will support a variety of niche missions. Their small launch mass and ultra-low cost will enable cost-effective solutions to new missions, such as sensor arrays or fractionated architectures where a larger number of satellites is needed.

Nanosatellite Development Activities

As an element of Boeing’s development activities in nanosatellites and picosatellites (mass less than 1 kg), engineers for Boeing Phantom Works’ Advanced Network and Space Systems (ANSS)—a component of Boeing Integrated Defense Systems—are using picosatellites as on-orbit test beds to evaluate new components and novel design approaches needed for future mission-capable nanosats. The company’s CubeSat TestBed 1 (CSTB1) was launched April 17, 2007, to validate a number of enabling technologies and nontraditional design elements. We use a small, dedicated team of sharp young-minded engineers in order to focus on the unique problems of developing these ultra-low power miniature spacecraft. A couple of the engineers have come from universities that were building CubeSats.

Validating Miniature Spacecraft Technologies

Because of the very low cost of developing and launching a CubeSat, we are able to perform this work using independent R&D funds. The CubeSat standard represents a great low-cost approach to quickly gain experience in fabricating such miniature satellites. Development started on CSTB1 in May 2005 and was delivered (after over a year of launch delays because of launch vehicle issues) in January 2007 for dispenser integration and for subsequent launch in April 2007.

The work on CSTB1 was done at the company’s Huntington Beach, Calif., campus in a new facility specifically created to work on these miniature spacecraft. Since they are so small, very little work space is needed, and as a result, all of the key development and testing can be done in the NanoSat Engineering Development Center (EDC). In order to further facilitate a highly integrated development environment, the EDC also contains the ground station that operates the spacecraft while in orbit. The complete system of spacecraft and its ground station were tested together throughout the development, integration and testing processes. Another great aspect of leveraging the CubeSat infrastructure is exploiting some of the nontraditional methods to keeping program costs low. For this initial test bed, the EDC used commercially available radios and software as elements of the ground station to communicate with the spacecraft. This small satellite ground station can support a variety of experimental missions and is now going through a significant upgrade that includes a 5.4-meter (17.7-foot) dish to accommodate missions needing higher communications bandwidth.

A lot of capability has been “shoe-horned” into the 900-gram CSTB1 satellite. There are a total of four microcontrollers in the spacecraft, with one having over 300 million instructions per second performance, redundant communication systems with two independent radios, two redundant high-capacity lithium-ion rechargeable batteries, a deployable antenna, an attitude determination system using sun and magnetic field sensors, and a simple attitude control capability using magnetic torque coils. The side panels of the spacecraft comprise multifunctional boards that contain a variety of sensors and electronics.

Since its launch over two years ago, CSTB1 continues to operate and has downloaded more than 1 million data points and dozens of images. It completed its entire primary mission goals within four months of operation, though continues to operate and surpassed 10,000 orbits March 4, 2009.

CubeSat CSTB2 and Beyond

Recently, a unique opportunity required that the Boeing NanoSat Team develop a new CubeSat (CSTB2) very quickly. In less than 10 weeks and supporting the project part-time, the team designed and fabricated the structure and electronics, as well as developed the needed software. Although this totally new CubeSat is a simple spacecraft design, by leveraging the rapid prototyping tools and processes utilized for our nanosat development, we were able to demonstrate our quick reaction capability in responding to this “pop-up” opportunity. Though the launch opportunity went away, the team demonstrated quick response capability that allows testing components and systems in a more risk-tolerant environment and for a very affordable price.

In addition to developing the knowledge of building and operating nanosatellites, an added benefit of the low-cost nanosatellite activities is that it enables a capability for other, larger spacecraft programs to quickly, and for low cost, evaluate components in orbit prior to their use on production programs.

Current activities are leveraging the lessons learned from CSTB1 and other development activities to designing and fabricating the next test bed vehicle “CSTB3,” which represents significant improvements in all of the subsystems. CSTB3 will utilize a triple or 3U CubeSat form factor and will validate a number of new technologies that include precision onboard attitude determination and control, and ultra-low power avionics. This size of nanosat is a more popular size because of the increased volume, mass and power available for payloads. Typical payload accommodations are roughly half the volume of the 10 by 10 by 30 centimeter spacecraft size, approximately 1.5 kilograms (3.3 pounds), and up to 20 W at 50 percent duty cycle. In addition, this larger 3U spacecraft “bus” can provide higher communications bandwidth (greater than 100 kbps), and more precise pointing (less than 0.1 degree) using miniature star trackers and reaction wheels.

Why of Interest

With the on-orbit success of PicoSat CSTB1 and the quick response of CSTB2, organizations within the government now have at their disposal a low-cost, quick-response option to test in orbit small components and subsystems for their space programs. There is a large number of sensor or spacecraft development programs that could benefit by using an early, low-cost experiment to reduce risk by testing the component in space.

The ultra-low cost of CTSB1 allowed the team a higher tolerance to risk to enable experiments with more radical design elements that wouldn’t occur with a more traditional program. Leveraging the experience from this project and the flight-validated design elements, the NanoSat Team can utilize these elements in new, more capable designs to support emerging nanosatellite missions. A key enabler to the small packaging needed with a nanosatellite is a highly integrated design. The current CubeSat design utilizes multifunctional side panels that can support a variety of embedded mission sensors, which significantly helps in facilitating a highly integrated nanosatellite design.

Background on CubeSats

In 1999, a spacecraft standard was jointly developed by professors Dr. Bob Twiggs of Stanford University and Dr. Jordi Puig-Sauri of California Polytechnic State University (Cal Poly) for a picosatellite with the goal of reducing time for their students to develop spacecraft for educational purposes. With students graduating without seeing the products of their labor being launched, it was felt that a standard spacecraft design would reduce the time from the five years or more that it was typically taking. (Does this sound familiar?) This “CubeSat” standard (http://cubesat.calpoly.edu/) has been extremely successful, with currently well over 100 colleges, universities and other organizations around the world engaged in development of spacecraft to this specification, and openly sharing information and collaborating on their work. The CubeSat specification defines key requirements (e.g., shape of a 10-cm cube, less than 1 kg, must be powered off during launch, must pass qualification thermal vacuum and vibration tests), and by following the specification, users can leverage the CubeSat infrastructure (e.g., e-mail exploder, Websites, regular workshops, and group-coordinated launches). This significantly reduces the cost and development time of designing, fabricating and launching spacecraft into orbit.

To advance the use of CubeSats, Cal Poly has developed and flight-qualified a dispenser (P-POD) that holds up to three 1U CubeSats or a single 3U CubeSat, further reducing the coordination effort needed to get a CubeSat launched. In addition, Cal Poly is actively brokering launches for the CubeSat community for typically $40,000 to $80,000 per 1U CubeSat, depending on the specific launch. This extremely low cost makes access to space very affordable to organizations or programs with very limited budgets. Cal Poly is currently coordinating several future launch opportunities and is in discussions with several U.S. launch vehicle companies to provide future domestic launch opportunities. Due to their very small size, it is often questioned as to the usefulness of CubeSats with the volume for the payload within the 1U CubeSat, which is typically less than a few hundred cubic centimeters, with mass less than 400 grams, and electrical power that is typically less than 700 mW. A CubeSat developed by the University of Tokyo has been in orbit since 2003 taking pictures of the Earth using a miniaturized camera similar to what is used in cell phones. In addition to using CubeSats as component test beds, they can also perform useful scientific experiments. Planned CubeSat payloads include a variety of different space weather sensors to augment existing science missions with additional data from different orbits to provide a larger spatial understanding of the environment around the Earth. ♦

Editor’s Note: Scott MacGillivray is the manager for Nano-Satellite Programs at Boeing Phantom Works.

Back to Top