SUMMARY OF OUR SOLUTION
In one embodiment, a satellite is constructed with a system having an orbital debris tracking subsystem to detect and track objects using a microwave or light (LADAR) frequency radar or similar sensors/detectors. Detection and tracking equipment can include higher frequency microwave or laser radars, which may be preferable under certain circumstances because their resolution of debris size and motion is better, the required antenna on the satellite will be smaller and atmospheric attenuation is not a problem (since the satellite and debris are typically well above the atmosphere). The satellite has onboard computer capability which calculates from its radar/ladar data and from data on its own orbit (derived from onboard sensors such as star, earth and sun sensors, GPS receivers, and/or from stored data sent from its ground control station through the satellite’s command subsystem) if a collision could occur. If a collision would be likely, the computer calculates the minimum change in the satellite’s orbit to avoid such collision and generates commands for firing on-board orbital control thrusters to put the satellite in an avoidance orbit. Other than the radar/ladar, most large, modern communications and broadcast satellites currently have the aforementioned onboard sensors and a propulsion system with thrusters.
Detection, tracking and autonomous debris avoidance from a satellite is fundamentally superior from doing it elsewhere including from earth stations. Debris orbits are random and numerous, resulting in potential collision paths from anywhere in the spheroid around the satellite. Smaller, rapidly moving debris are particularly difficult to detect from earth stations which are often also limited by non-continuous coverage and by the inability to penetrate the atmosphere efficiently at various frequencies such as optical. Since, in many cases, avoidance must be accomplished in a very short period, autonomous operation in the satellite is faster than doing the same operations from earth station(s) due to command transit time between the station and satellite and other previously mentioned factors.
The description following of autonomous debris avoidance operations is described in terms of separate computer processors. In fact, these are software programs. The best way to implement them would be based on the computer/processor equipment on a particular satellite. Since many of the bigger satellites already have large computers with big memories, many or all of the debris avoidance software programs could be integrated into these computers or their modest expansions for this purpose.
The loss of a large satellite due to debris collision would be a very major operational and economic disaster. Operationally, large commercial communications and broadcast satellites each may serve millions of customers. Little spare on orbit satellite capacity exists, and these satellite operators generally have no alternatives, especially from an unplanned event. Particularly note that the production and launch of a replacement satellite of this type takes at least 3 years and often more. The cost of replacement is at least a quarter of a billion US dollars plus the risk of a replacement satellite launch failure.
In addition, the orbit determination processing means is adapted to provide debris orbital elements data of the debris including semi-major axis, eccentricity, inclination, right ascension of ascending node, argument of perigee, period, time of perigee and their variances. Furthermore, the ephemeris processing means is adapted to calculate location ephemeris data for future positions of the debris relative to future positions of the satellite. Moreover, the collision calculation means is adapted to receive the location ephemeris data for a piece of debris and the location ephemeris data for the satellite from the ephemeris processing means.
Current satellite designs include low thrust, high efficiency electrical propulsion thruster to realize stationkeeping operations. Since these systems are only capable of small orbital adjustments, orbital corrections must occur at frequent intervals, sometimes twice per day. In light of consideration of planned, nominal orbital adjustments, the ephemeris processing means must therefore be aware of ongoing, or imminent station keeping operations when considering future possible collisions. In general, collision avoidance may be achieved with the addition of a collision avoiding orbit adjustment, the removal of one or more nominal stationkeeping adjustments, or a combination of both.
The collision calculation means is also adapted to provide a collision conclusion showing whether a collision would or would not occur at some future time between a piece of debris and said satellite. In addition, the satellite avoidance orbit processing means is adapted to receive output from the collision calculation means and to calculate a minimum change of the satellite’s existing orbit to an orbit which avoids collision with said debris. Furthermore, the satellite avoidance commands processing means is adapted to receive the data for a minimum change in orbit, to calculate the required commands for the satellite thruster firings and to cause these commands to be executed.
The data on the mapped orbital debris in the spheroid around the satellite (as well as the trajectory data on debris which might collide with the satellite) can be sent to a ground control Earth station through the satellite’s telemetry subsystem. The data on the mapped debris will contain other objects in the space around the satellite including other operational satellites, non-operational satellites, meteors, inspector satellites, etc. These data can be used to provide enhanced space awareness.