Analytical Graphics Inc. | Date: 2016-07-07
Systems, methods, devices, and non-transitory media of the various embodiments provide for a volumetric approach to determining orbital encounters that may determine the number of encounters over a specified length of time. Such information may be used to determine how often during an orbit or period of time an object might trigger a conjunction warning for a neighboring satellite. The various embodiments may be used as a planning and characterization tool to estimate satellite encounter rates for a prospective orbit regime and may provide an efficient, in-line approach to assess the number of encounters occurring within a user-specified span of time.
News Article | July 12, 2017
Back in February an Indian Space Research Organization rocket deployed over a hundred miniature spacecraft into Earth orbit. This constituted the largest stream of petite satellites, called CubeSats, ever dispensed into space courtesy of a single heave-ho booster—but not by much. Seventy more are slated to hitch a ride onboard a Russian rocket later this week. In launches large and small, on the order of 700 CubeSats have made their way into space since the late 1990s, and the pace is picking up. CubeSats are a distinctively low-cost class of nanosatellite that can weigh less than three pounds and come in a standard size and shape. The average CubeSat size is “one unit” or “1U” measuring 10 X 10 X 10 centimeters, but can be upsized to 1.5, 2, 3, 6 or even 12U. This flexibility makes CubeSats a bargain compared with full-size satellites, with a wide range of costs. For instance, a simple CubeSat built by students or hobbyists might cost roughly $50,000 whereas more advanced projects from professional aerospace companies can range from $250,000 up to $2 million. A CubeSat’s utility in space seems limited only by its size and the imagination of its designers and users—governments, universities and private companies increasingly rely on them for everything from broadband remote monitoring of Earth to performing on-orbit science experiments as well as test-flying novel propulsion and communications technologies. As the number of CubeSats and other orbiting nanosatellites continues to rise, so too do debates about their most important effects: Are CubeSats really the vital educational, scientific and technological tools that their staunchest proponents insist they are—or are they mere indulgent toys irresponsibly adding to the menacing shell of litter already encircling the planet? It is already a well-known mess. Orbital debris is the term for any object in Earth orbit that no longer serves a useful function. This clutter of the commons is a mix of dead spacecraft, spent rocket stages, steel bolts, paint chips and even frozen bits of nuclear reactor coolant. A hypervelocity run-in with space rubbish can take out or cripple an expensive satellite or even threaten the safety of a vehicle’s crew. A recent study led by Hugh Lewis, an aerospace engineer at the University of Southampton in England, reports the growth of small satellite traffic is expected to have a “significant impact” on the space environment. “From my perspective, there are two sides to the story…at least,” Lewis says. “CubeSats are being launched in greater numbers partly because they represent a cost-effective solution to an engineering or commercial problem. In particular, there are growing demands for Earth observation data and communications, which can be met through the use of CubeSats at relatively low cost. The challenge for regulators is to develop and apply rules that enable these services and benefits to be realized in a sustainable manner. I think it is fair to say that this is not an easy task.” Lewis’s study suggested a need to consider additional space debris mitigation guidelines for CubeSats. Under an international agreement called the “25-year rule” countries acknowledge they should not launch objects whose life span in Earth orbit will go beyond 25 years after their mission concludes. Compliance, however, is voluntary; countries can choose to implement it (or not) for launch vehicles lifting off from their territories. The U.S. government does not approve any launch violating the 25-year deorbit rule. For U.S.-launched CubeSats, this usually means placing them in an elliptical or low-altitude orbit from which they will drift downward and burn in the atmosphere after seven years or less. But the big picture—for both big-time and small-time space players—is there is no enforcement of this rule. Evidence from the past decade has shown satellite operators to have a “patchy record” of compliance, at best. The study advises that enforcement could help mitigate the impact of small satellites on the space environment—but the researchers add a caveat: Imposing restrictions on small satellite missions might inhibit creativity and perhaps have a cost impact that could derail the commercial viability of missions. CubeSats have proliferated because of their low cost, says Holger Krag, head of the European Space Agency’s Space Debris Office based in Germany. Krag adds, however, this is not a problem as long as everyone follows space debris mitigation guidelines like the 25-year rule. Our simulations have shown that even [an] increased amount of CubeSats can be absorbed by the environment if launched into low-enough orbits,” Krag says. “Of course, there is a natural limit to this, which has not been quantified as yet, and increased traffic in low altitude means more interference with the operations of the International Space Station.” NASA and the international community are concerned about the environmental damage CubeSats could cause, says Don Kessler, a retired NASA senior scientist whose name will forever be enshrined in the pantheon of space junk specialists. In 1978 Kessler detailed how debris-creating satellite collisions and explosions in orbit could kick off a chain reaction that exponentially increases the amount of space junk whirling around the planet. Such a “Kessler syndrome” could easily render spaceflight too hazardous to conduct. Kessler says CubeSats’ small size is a plus, because they simply contain less material that could be transformed into spacecraft-threatening debris. But this is offset by other factors including their great numbers and their limited reliability and maneuverability. Their proliferation may require new mitigation rules, particularly because some might be too small to be adequately tracked from the ground. “The services they could provide at a low price are positive attributes,” he says. “But they also represent a new challenge to maintaining a sustainable environment.” On one hand, the spacecraft community is aware of these challenges and is attempting to address them. On the other, “my additional concern is that the modeling of the large constellations of CubeSats is inadequate,” he adds, referring to computer simulations used to predict and analyze potential technical problems. Although at least one model includes space junk items as small as one centimeter, most long-term models predict growth only in the 10-centimeter and larger category, Kessler explains. “However, CubeSats are highly vulnerable to much smaller debris, with collisions resulting in even more nontrackable debris and potentially contributing to cascading within the constellation as well as with any nearby large constellation.” Kessler notes he has already voiced his concern over this issue. There has been a noteworthy increase in the use of CubeSats and other small satellites for a variety of space missions, says George Nield, associate administrator of the Federal Aviation Administration’s Office of Commercial Space Transportation. And for good reason, Nield says: because of their lower costs, CubeSats offer a major opportunity for increased innovation. They can fly more frequently and for less money to hone novel concepts, potentially unlocking new products, services, customers and markets faster and cheaper than any traditional satellite system. “However, it is important to note that there are several challenges that need to be addressed in order to take full advantage of those potential benefits,” he suggests. “For example, because of their size the satellites themselves can be difficult to track, and they are frequently not maneuverable. At the same time, because they are intentionally designed to be low in cost, most of these satellites have limited or no redundancy and only marginal reliability.” As a result, many of these systems become orbital debris shortly after they are launched, he says. “If we want to be responsible stewards of the space environment,” he adds, “we need to think about how we can enable these systems to operate in space while ensuring that they do not become hazards to other space operators.” Nield points out that some ideas already exist for minimizing debris risks from the proliferation of CubeSats, such as: —Encouraging the use of orbital altitudes and inclinations that decrease the chance of collisions with the International Space Station and other high-value facilities. —Identifying the best methods for reducing CubeSat orbital lifetimes. —Adding beacons, transponders or corner reflectors to each spacecraft so they become easier to track. CubeSats offer a number of challenges, says Brian Weeden, a former officer in the U.S. Air Force with a focus on space security and current director of program planning for the Secure World Foundation. First, CubeSats are now relatively hard to track and conclusively identify. Often deployed in clusters, most lack distinguishing features and have limited or no maneuverability to actively avoid collisions, Weeden explains. Moreover, CubeSat operators may have little to no experience with using satellites, he continues, noting some CubeSats are being launched by countries that may not have much national regulation or oversight in place. He thinks the identification challenge is more pressing than the tracking one—although the two are interlinked. A 10-centimeter CubeSat is trackable with existing sensor networks, he says, “but if you dump dozens of them out at the same time, it can be really tough to tell which one is which.” Several ways to establish satellite “ID tags” have been proposed, Weeden says, but he is unaware of any effort to assess which ones are the most effective or to develop them into working solutions. “I'm skeptical of getting much progress from the government side in the near term,” he says. “The zeitgeist in Congress and the [Pres. Donald] Trump administration right now is all about getting rid of regulations and reducing the size of government. In fact, there have been prominent members of Congress openly questioning whether the U.S. government needed to provide any regulation of space activities at all.” That said, Weeden adds that the CubeSat and commercial space community seems to be taking these issues seriously. This community includes CubeSat operators who are “keen to be responsible space actors,” he says. T. S. Kelso, a senior research astrodynamicist for Analytical Graphics’ Center for Space Standards and Innovation, views CubeSats as a positive development—especially in encouraging university participation and stimulating creativity. “And I think some of the ‘big data’ applications have the potential to be truly game-changing for our society,” he adds. Kelso notes that the creators of the CubeSat standard chose the 10-centimeter unit size based largely on what the community understood the Pentagon’s Space Surveillance Network could track—because knowing a satellite’s location is key to using it. “Unfortunately, the Department of Defense resistance to discussing capabilities and pointing out the difficulties of tracking objects of this size has left us in a situation where this is still a challenge,” he says. When that challenge is combined with projects that deploy 30 or more CubeSats, “trying to associate observations with tracks and generate good orbits becomes even more difficult,” Kelso explains. It can take military space watchers weeks to sort out each CubeSat’s orbit, he says, and failure to be able to track and identify objects can prevent operators from being able to perform key activation tasks and result in the loss of a satellite. “Unfortunately, most operators are unaware and unprepared for this problem, since they believe that the U.S. has it ‘all under control.’ They often don’t understand the problem until after launch when they are scrambling for help,” he says. “The community needs to be informed of this challenge, and then work together to find creative ways to address it. And the U.S. government—or even nongovernmental entities that operate large networks of satellites—might want to fund use of a solution to prevent these educational tools from simply adding to the debris population.” For now CubeSats’ popularity is clearly on the upswing. First used as teaching tools and for technology demonstrations, their utility to perform more complex science duties and serve as the backbone of commercial services is gaining traction. What remains to be seen is whether or not their proliferation adds to the heavenly headache of dealing with the escalating hazard of Earth-orbiting debris.
News Article | November 14, 2016
Editors Note: There are two photos associated with this press release. Thoth Technology Inc. in partnership with Analytical Graphics Inc.'s Commercial Space Operations Center (ComSpOC) has developed a deep space radar system for the detection of objects orbiting over North America. Designed to detect and protect key space assets in geostationary orbit, the system also has the capability to locate other space objects including the moon. The team refurbished Canada's largest antenna, a fully steerable 46m dish in Algonquin Park, equipping it with a modern space situational awareness (SSA) system capable of locating targets to within 25 meters. "Space is our business," said Caroline Roberts, CEO of Thoth. "Our new SSA system can provide real time warning of incoming space objects and also detect faults in geostationary spacecraft," she said. As part of Thoth's calibration activity, the SSA system tracked the moon for approximately two hours during its close approach to Earth. "Although it's closer than it's been since 1948, it's still more than 350,000 kilometers from Algonquin Park, and to me that's not that close. It takes the radio waves more than 2.3 seconds to travel to the moon and back to the observatory," said Brendan Quine, Thoth's CTO and the system's designer. "The moon is a great calibration target for us, and it's so beautiful when it is this bright. We should be able to learn a lot about the moon from the data," he said. Thoth plans further enhancements of its SSA capability to include imaging of space objects shortly. To view the photos associated with this press release, please visit the following links:
Tanygin S.,Analytical Graphics Inc.
Journal of Guidance, Control, and Dynamics | Year: 2013
This paper examines the projective geometry of three-parameter attitude representations that are constructed by projecting a four-parameter unit quaternion representation from its unit hypersphere onto a three-dimensional hyperplane. Using this geometrical perspective, the paper demonstrates how kinematics of relative attitude motion characteristic of attitude tracking problems follow naturally from comparing projections from two different reference directions. The paper also demonstrates that among a continuum of possible projection pole placements there exist optimal distances for which resulting projected parameterizations yield magnitudes that accurately approximate all practical rotation angles. These parameterizations referred to in this paper as proxy-rotation vectors can be custom tuned for any expected range of rotation angles. They and their kinematics are free from trigonometric functions and do not require special handling if the rotation angle approaches zero. It is shown that this computational simplicity of the proxy-rotation vectors can be advantageous for linear feedback attitude controls and for certain classes of time-efficient attitude steering laws, where they can replace the more computationally cumbersome true rotation vector. The paper studies how kinematic singularities affect closed-loop stability and demonstrates that redesigning control laws to ensure closed-loop convergence toward the nearest equilibrium is equivalent to augmenting attitude parameterizations with their shadow counterparts. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Tanygin S.,Analytical Graphics Inc.
Journal of Guidance, Control, and Dynamics | Year: 2012
A class of vectorial attitude parameterizations that are formulated as a product of the unit rotation vector and various functions of the rotation angle is examined. When related to a four-dimensional unit quaternion, these vectorial parameterizations are shown to be analogous to higher-dimensional azimuthal projections from a threedimensional unit hypersphere. Several types of these projections are examined. Singularities are identified and numerical accuracy is evaluated based on the singular value decomposition of the attitude kinematics. It is shown how shadow parameterizations can be constructed in order to alleviate the kinematical singularities. It is also shown that the kinematical passivity and optimality of the Rodrigues and modified Rodrigues parameters are special cases of the more general result that holds for a wider range of vectorial parameterizations. This result is used to formulate and compare passivity-based control laws using various parameterizations. Copyright © 2011 by Sergei Tanygin. Published by the American Institute of Aeronautics and Astronautics, Inc.
Analytical Graphics Inc. | Date: 2012-01-11
Determining a launch window from anywhere within a specified area to avoid or minimize close approaches between a launch vehicle and orbiting space objects. A method and apparatus is disclosed for minimizing close approaches, or conjunctions between spacecraft being launched from anywhere within a specified area and other objects in space during the launch and early deployment phase of their lifetime, by defining a launch window, utilizing and identifying launch window blackout times to avoid close approaches of launch trajectories from anywhere within an area with remaining objects in space as noted in a space object catalog.
Analytical Graphics Inc. | Date: 2014-09-03
Methods, systems, and devices for the visualization of the region of a 3-dimensional space obstructed from a viewing location by an ellipsoid are disclosed. In an embodiment, the obstructed region may be defined from primitive elements which are combined using Boolean operations. The primitive elements chosen may be represented using both implicit functions and/or parametric surfaces. In an embodiment, the implicit function representation may be used to quickly determine points on candidate surfaces which may be obstructed from view. In an embodiment, the parametric representation may be used to provide ray-surface intersection solutions enabling visualization of the boundary surface of the obstruction region.
Analytical Graphics Inc. | Date: 2013-12-20
A device and method for presenting augmented image data. An image capture device captures an image together with information about the image. Alternatively a data logger may capture additional information about a particular image. The image and additional information is sent to a database where a server analyzes the augmented image and relates the augmented image to other images in the database. A subsequent user may query the database for all images and augmented information for a particular area, location, or object and retrieve that collected information for subsequent analysis.
Analytical Graphics Inc. | Date: 2013-02-28
A device and method for displaying data simultaneously in two-dimensional and three-dimensional formats. A user selects data to be represented in multiple formats simultaneously. A data rendition server retrieves the data and determines the three-dimensional representations that are possible. The user then selects the three-dimensional representation desired, and the server renders the data to the user in both two-dimensional and three-dimensional formats. The data may be rendered together with static data such as digital terrain data and other static data types. Data representations may be rotated and morphed as desired by the user.
Analytical Graphics Inc. | Date: 2014-10-22
A computing device may detect that a space object has undergone a maneuver and may attempt to calculate a solution to that maneuver based in part on start and stop times and thrust uncertainties associated with the detected maneuver. However, the computing device may sometimes be unable to calculate an acceptable solution for a detected maneuver given these initial start and stop times and thrust uncertainties. Thus, the various embodiments provide for a computing device and methods implemented by a processor executing on the device for identifying and calculating a recovery maneuver of a space object when an acceptable solution for a detected maneuver cannot be determined. In the various embodiments, a computing device processor may generate a recovery maneuver based on the detected maneuver, and the processor may adjust the start and stop times and the uncertainty values of the recovery maneuver until an acceptable solution is found.