Technical Sessions

Session X: The Smaller Elements

Chair: Jamie Cutler, University of Michigan

Wednesday, August 12, 2009 

3:45 p.m. The IRIS Nanosatellite for Autonomous Multi‐System Responsive Space Operations and High Spectral Resolution Earth Imaging

Erin Beck, Christopher Kitts, Jose Alberto Rosales Cruz, Alexander Fischer, Steven Li, and Anthony Young – Robotic Systems Laboratory/Santa Clara University

ABSTRACT: Santa Clara University’s Robotic Systems Laboratory is developing the Intelligent Responsive Imaging Spacecraft (IRIS) for autonomous multi‐system responsive operations and high spectral resolution Earth imaging. IRIS will interact with an extended system of land, sea, air, and space‐based robotic and human elements to observe transient events on the ground. Specifically, IRIS will provide critical imaging and communications services to detect, monitor, and respond to harmful algal blooms in shallow water regions. Students are responsible for all aspects of development. This paper will describe the mission concept and its use of advanced small satellite technologies to perform multi‐system responsive space operations.

4:00 p.m. Enabling Flexible Secondary Launches with the CubeSat Standard

Jordi Puig‐Suari, Roland Coelho – Cal Poly; Kyle Leveque, Victor Aguero, Scott Williams – SRI International

ABSTRACT: CubeSats are currently forced to follow the traditional secondary payload model. In this model secondary payloads must identify a particular launch opportunity with a primary. The secondary payloads must commit to the launch and are subjected to any delays solely due to the primary. Additionally, this secondary payload paradigm is forcing suboptimal use of excess launch capacity since it complicates the process to add additional secondary payloads close to the launch date. This situation does not scale to support the growing demand for CubeSat launches that could potentially reach 100s of CubeSats per year within the next few years. A more flexible secondary launch model is required to support the CubeSat community and provide the fast access to space made possible by the CubeSat standard. This flexible model will allow developers to focus on the development of their spacecraft. Several key developments are necessary to reach a truly flexible secondary launch capability including technical, political, and regulatory issues. Some of the most critical are currently being addressed by work being performed by Cal Poly and their industrial and government partners.

4:15 p.m. SMDC‐ONE: An Army Nanosatellite Technology Demonstration

David Weeks – COLSA, Inc.; Brent Marley – Cobham Analytical Services, Inc.; John London – US Army Space and Missile Defense Command

ABSTRACT: Our nation has a truly impressive array of space‐based capabilities supporting our armed forces. However, much of this support is focused at the strategic and operational levels of war. There are several areas of desired improvement in the space force enhancement mission area at the tactical level of war that could be addressed by small, inexpensive satellites dedicated for use by tactical land warfighters. One of these areas of desired improvement is tactical beyond‐line‐of‐sight (BLOS) communications, including support for ground sensors, text message relay, voice communications, and image or video transmission. Technical solutions to fill these areas of desired improvement should be relatively inexpensive, and more importantly, taskable by tactical users in the area of operations.

New trends in the miniaturization of electronic components are leading to smaller satellites with significant capabilities in the nanosatellite (1‐10 kg) and microsat (10‐100 kg) classes. For example, the CubeSat standard for nanosatellites now being built by universities around the world is based on tiny cube‐shaped satellites with dimensions of only 10cm on a side and weighing about 1 kg. Slightly larger nanosatellite configurations, with multiple cube formats, allowing for missions from low earth orbit with broader scopes are under investigation by organizations such as NASA, Boeing, and the US Army.

One technical approach that could address today’s tactical BLOS communications area of desired improvement for the tactical warfighter would be a constellation of nanosatellites in low earth orbit. To investigate the feasibility of such a constellation, the US Army Space and Missile Defense Command/Army Forces Strategic Command (USASMDC/ARSTRAT) is executing the Space and Missile Defense Command – Operational Nanosatellite Effect, or SMDC‐ONE, technology demonstration. The key SMDC‐ONE demonstration thresholds for success involve designing, developing, building and qualification testing of two nanosatellite units, and acceptance testing of eight flight units within a one‐year timeframe ending in April 2009. A custom communications payload will deliver a capability to support simulated ground sensors and text message relay. Communications beyond this level of complexity were not included in this demonstration to reduce schedule risk. SMDC‐ONE can help establish the case for inexpensive space force enhancement for the tactical warfighter through relatively inexpensive, rapidly developed nanosatellite constellations.

4:30 p.m. Pointing Control for Low Altitude Triple Cubesat Space Darts

James Armstrong, Craig Casey, Glenn Creamer, Gilbert Dutchover – US Naval Research Laboratory

ABSTRACT: Pointing control of cubesats can be quite challenging due to constraints on volume, cost, and complexity of control hardware. Recent achievements and developments in small sensor and actuator designs have enabled the possibility of reasonable pointing performance (a few degrees or better) for a variety of intriguing space experiments. In this paper we describe a simple pointing control design that exploits the aerodynamics associated with the space dart geometry of a triple cubesat with deployable solar panels in a low‐altitude orbit (< 500 km) to provide passive pitch and yaw stabilization, coupled with a small momentum‐biased pitch reaction wheel offering passive yaw and roll stabilization. Augmented active rate damping is provided using a small three‐axis magnetometer, three small magnetic torquers, and a model‐based B‐dot control law. This simple passive/active control system offers experiment pointing capability to less than 5 degrees of nadir without the need for any attitude knowledge.

4:45 p.m. “Coach Class to Orbit:” the NPS CubeSat Launcher

Christina Hicks, Adam DeJesus, Anthony Harris, Matt Crook, Felix Rossberg, Daniel Sakoda, Rudolf Panholzer, James Newman – Naval Postgraduate School

ABSTRACT: To meet the challenge of improving CubeSat access to space, a team of graduate students at the Naval Postgraduate School (NPS) is developing the NPS CubeSat Launcher (NPSCuL). NPSCuL is an enabling technology that seeks to utilize excess capacity on US launch vehicles to provide CubeSat developers with routine, high capacity, low‐cost access to space. The launcher currently integrates eight Cal Poly Poly‐Picosatellite Orbital Deployers (P‐PODs) with a deployment sequencer in a simple structure. NPSCuL will be able to accommodate up to twenty four units of CubeSat volume on a single launch using only one ESPA‐class payload interface. This capability has the potential to advance US space technology and ensure that the next generation of US space professionals will remain on the cutting edge of very small satellite development. A flight‐qualified NPSCuL is expected to be complete in late 2009 with a potential launch as early as August of 2010. NPSCuL provides “coach‐class‐to‐orbit:” a high‐capacity, low‐cost way to deliver CubeSats to space that is consistent with US launch capability, the CubeSat specification, the needs of the growing CubeSat community, and US national interests.

5:00 p.m. Boeing’s CubeSat TestBed 1 Attitude Determination Design and On‐Orbit Experience

Michael Taraba, Christian Rayburn, Albert Tsuda, Scott MacGillivray – The Boeing Company

ABSTRACT: The CubeSat standard has provided space access to rapidly accelerate the maturity of hardware components and software algorithms for extremely small satellites. The Boeing CubeSat TestBed 1 (CSTB1) on‐orbit experiment, launched April 17, 2007, validated a highly integrated and multi‐functional approach for attitude determination. This paper covers the constraints and design concept of a CubeSat attitude determination system using multiple integrated sensors. The on‐orbit data collected from five two‐axis commercial‐off‐the‐shelf MEMS magnetometers, and four suites of sun sensors was processed and analyzed to determine the attitude of CSTB1. The attitude determination was verified via an image from a low power CMOS camera and solar cell measurements. Lastly, this paper addresses how our attitude determination solution was used to help refine vehicle operations.

5:15 p.m. Increasing the Accuracy of Orbital Position Information from NORAD SGP4 Using Intermittent GPS Readings

Michael Greene, Robert Zee – Space Flight Laboratory/University of Toronto

ABSTRACT: Paramount to any satellite mission is the acquisition of accurate vehicle position and velocity information at any particular point in time. With several satellite tracking and propagation methods available, the use of the Two‐Line Elements (TLEs) supplied by the North American Aerospace Defense Command (NORAD) in conjunction with the Simplified General Perturbations Satellite Orbit Model 4 (SGP4) is considered the most popular choice for many low‐Earth missions. This is primarily due to the fact that the SGP4 algorithm is open‐source and that the TLEs are readily available to the public. Furthermore, they are updated on a fairly consistent – albeit infrequent – basis. If a particular mission requires more stringent accuracy than the SGP4 model can provide, an on‐board GPS receiver is often a natural choice. GPS receivers can provide much greater orbital position knowledge at the cost of consuming relatively large amounts of power. This paper describes a technique for increasing orbital determination accuracy through the SGP4 model using a GPS receiver for intermittent orbital information, complemented with a TLE from the most recent epoch. The goal is to increase the precision of the estimates obtained from SGP4 with an effort to minimize the duty cycle required by an onboard GPS receiver. This propagation technique is primarily geared towards nanosatellite‐scaled missions with regards to stringent power and antenna pointing requirements.