Abstract:
A ground-based laser ranging system and method are provided that enable meter-level or better ranging precision on optically passive 10-30 cm average-sized orbital debris targets. The system and method can improve current predictions by up to 85%. The improved location accuracy also provides the immediate benefit of reducing costly false alarms in collision predictions for existing assets and unidentified debris. The system can include one or more high power lasers that generate 1.5 μm wavelength laser pulses at &gt;100 mJ pulse energies and at a repetition rate of from 10 Hz to 100 Hz.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0001]    The invention described herein was made in part by employees of the United States Government and may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a system and method for identifying and tracking orbital debris. 
       BACKGROUND OF THE INVENTION 
       [0003]    The mitigation of orbital debris was addressed in the most recent release of the National Space Policy directing space faring agencies to pursue technologies that will mitigate and remove on-orbit debris. No matter what abatement technology is developed and deployed, a remote sensing infrastructure to locate and track these objects with adequate precision is still lacking. 
         [0004]    Orbital debris has become a national and worldwide issue for orbital assets, past, future and present, a risk to manned space flight and the International Space Station (ISS), and an ever-increasing hazard to Earths citizenry due to uncontrolled reentries of dead or wayward satellites. The amount of such debris is reaching a critical level, with current estimates of space debris with mean diameters of 1 cm or greater now exceeding 500,000. Worse yet, the number of critical-size space debris items with diameters of 10 cm or greater and enough impact energy to break up their target has reached about 21,000, with a total mass in orbit of nearly 6,000 metric tons. A catalog of these critical size debris objects is constantly monitored and updated, but with limited resolution. Unless the orbital characteristics of the debris object are known more precisely, the most effective debris removal and mitigation methods can do little more to address this problem than RF and passive optical techniques. Awareness of these risks are ramping up and efforts are underway to generate new technologies and methods for debris mitigation. 
         [0005]    Using ground based lasers to track orbiting objects is a well understood, and worldwide-employed technology, with various lasers, pulse characteristics, detection, and tracking schemes. These techniques are all typically used and performed daily across the globe to track “laser cooperative” objects. A “cooperative” object is defined as a satellite with retro-reflectors installed on its surface, and pointed in some fashion toward the Earth. This enables the high resolution ranging stations to operate with low power, visible laser wavelengths at eye safe parameters in concert with smaller, less expensive telescopes for the laser pulse return detection. In order to adapt laser ranging techniques to “uncooperative” objects, i.e., random orbiting debris, much larger optical collection techniques as well as greater laser pulse energies are required. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one or more embodiments of the present invention, a ground-based laser ranging system and method are provided that enable meter-level or better ranging precision on optically passive 10-30 cm average-sized orbital debris targets. The system and method is expected to improve current predictions by up to 85%. The improved location accuracy is also expected to provide the immediate benefit of reducing costly false alarms in collision predictions for existing assets and unidentified debris. In accordance with various embodiments of the present invention, it has been determined that the use of a Joule-class Nd: YAG laser at 1064 nm or 532 nm wavelengths can be used to track some uncooperative objects, but the impact on commercial aircraft forbids continuous or on-demand operations over most of the Earth. Thus, according to the present invention, using a joule-class laser in eye-safe wavelengths solves this problem. 
         [0007]    According to one or more embodiments of the present invention, the cooperative network includes one or more ground-based laser ranging facilities at least one of which includes a high power laser system that can deliver pulsed laser beams having a wavelength of from 1.4 micrometers (μm) to 1.9 μm, pulsed at a repetition rate of from 10 hertz (Hz) to 100 Hz. In some embodiments, the high power laser can comprise a dual head laser as disclosed in U.S. Pat. No. 8,958,452 B2 to Coyle at el., which is incorporated herein in its entirety by reference. In some embodiments, the high power laser can comprise an Nd: YAG oscillator, laser system, spacecraft, or combination thereof as described in concurrently filed U.S. patent application Ser. No. ______ to Stysley et al. entitled “Nd: YAG Oscillator-Based Three-Wavelength Laser System” (Attorney Docket No. GSC-17345-1), which is incorporated herein in its entirety by reference. The high power laser can produce pulse energies of 100 mJ or greater, TEM 00  beam quality, and low divergence, without requiring further amplification. Such high power lasers can provide improved resolution and tracking and can enable enhanced capabilities and accuracy of the orbital debris tracking cooperative network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present invention can be even more fully understood with the reference to the accompanying drawings which are intended to illustrate, not limit, the present invention. 
           [0009]      FIG. 1  is a graph showing the relative number of critical-sized (d&gt;10 cm) orbital debris objects, and showing the highest concentrations residing at altitudes of between 700-900 km above the Earth&#39;s surface. 
           [0010]      FIG. 2  is a schematic diagram showing a cooperative network of Orbital Debris Laser Ranging (ODLR), satellite laser ranging (SLR), and Debris Radar tracking facilities, and exemplifies the open sharing of data products, and the incorporation of Joint Space Operations Center (JSpOC) and Crustal Dynamics Data Information System (CDDIS) procedures and processes. The network greatly reduces the false alarm collision warnings with space assets and significantly increases the accuracy of identifying known objects and discovering many more. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    According to various embodiments of the present invention, a system of laser ranging tracking facilities for tracking an orbital debris target in low Earth orbit, is provided. The system can comprise a plurality of laser ranging stations comprising at least two ground-based laser ranging stations that can be separated from one another, for example, spaced around the globe or separated by one another by at least 100 miles. Each laser ranging station can detect an orbital debris target and can transmit to a central processor a respective signal indicative of the orbit of the orbital debris target. The system can include a central processor having a receiver configured to receive transmitted signals from the laser ranging stations. The processor can be configured to process the signals received by the receiver into data sets each pertaining to the orbit of a respective the orbital debris target. A datastore can be provided and configured to store the data sets pertaining to the orbit of the orbital debris target. At least one of the ground-based laser ranging stations can comprise a high power laser configured to provide laser pulses at a wavelength of from 0.5 μm to 2.5 μm at a pulse energy of 100 mJ or greater and at a repetition rate of from 10 Hz to 100 Hz. In an exemplary embodiment, the high power laser is configured to provide laser pulses at a wavelength of from 1.4 μm to 1.9 μm, at a pulse energy of 100 mJ or greater, and at a repetition rate of from 10 Hz to 100 Hz. For example, the high power laser can be configured to provide pulsed laser light at a wavelength of about 1.5 μm, for eye safe applications. High power lasers of such specifications can beneficially provide reliable tracking of orbital debris targets that are non-compliant, uncooperative, or both. 
         [0012]    According to various embodiments, the processor can be configured to process the data sets into orbital data pertaining to the orbit of the orbital debris target, store the orbital data in the datastore, and calculate a future orbit path of the orbital debris target based on the stored orbital data. The calculated future orbit of the debris target can be used to determine whether an existing low Earth orbit asset, such as a satellite, needs to be repositioned to avoid a collision with the orbital debris target. 
         [0013]    The system can further comprise at least one laser ranging satellite configured to detect an orbital debris target and transmit a signal to the central processor, which is indicative of the orbit of the orbital debris target. The receiver of the central processor can be configured to receive signals from the laser ranging satellite. The laser ranging satellite can comprise a high power laser configured to provide laser pulses at a wavelength from 1.0 μm to 1.9 μm at a pulse energy of 100 mJ or greater and at a repetition rate of from 10 Hz to 100 Hz, for example, a wavelength of about 1.5μm. The system can additionally, or alternatively, comprise a radio frequency radar station configured to track the orbital debris target and transmit a respective signal indicative of the orbit of the orbital debris target, to the receiver, and the receiver can be configured to receive signals from the radio frequency radar station. 
         [0014]    According to various embodiments, the system can additionally, or alternatively, comprise a passive optical tracking radar station configured to track the orbital debris target and transmit a respective signal indicative of the orbit of the orbital debris target, to the receiver, and the receiver can be configured to receive signals from the passive optical tracking radar station. According to various embodiments of the present invention, a method of tracking an orbital debris target in low Earth orbit is provided. The method can comprise laser ranging the orbital debris target using a plurality of laser ranging stations comprising at least two ground-based laser ranging stations. The at least two ground-based laser ranging stations can be spaced around the globe, for example, separated from one another by at least 100 miles. The method can involve transmitting a respective signal from each of the laser ranging stations, indicative of the orbit of the orbital debris target. The receiver can receive the transmitted signals from the laser ranging stations and a processor can process the signals received by the receiver into data sets each pertaining to the orbit of the orbital debris target. The data sets pertaining to the orbit of the orbital debris target can be stored in a datastore. At least one of the ground-based laser ranging stations can be configured to laser range with a high power laser that provides laser pulses at a wavelength of from 1.4 μm to 1.9 μm at a pulse energy of 100 mJ or greater and at a repetition rate of from 10 Hz to 100 Hz. In an example, the high power laser can provide pulsed laser light at a wavelength of about 1.5 μm. 
         [0015]    The method can use a processor that processes the data sets into orbital data pertaining to the orbit of the orbital debris target, stores the orbital data in the datastore, and calculates a future orbit path of the orbital debris target based on the stored orbital data. The method can further comprise laser ranging the orbital debris target with at least one laser ranging satellite and transmitting a satellite signal from the laser ranging satellite to the receiver. The satellite signal can be indicative of the orbit of the orbital debris target. The receiver can receive the satellite signal and process the satellite signal into a data set pertaining to the orbit of the orbital debris target. The laser ranging satellite can produce high power laser pulses at a wavelength from 1.0 μm to 1.9 μm at a pulse energy of 100 mJ or greater and at a repetition rate of from 10 Hz to 100 Hz. In an eye-safe example, the high power laser of the laser ranging satellite produces pulsed laser light at a wavelength of about 1.5 μm. 
         [0016]    According to various embodiments, the method can further comprise tracking the orbital debris target with a radio frequency radar station and transmitting a respective signal indicative of the orbit of the orbital debris target, to the receiver. The receiver can receive signals from the radio frequency radar station and process the signal received from the radio frequency radar station into a data set pertaining to the orbit of the orbital debris target. Additionally or alternatively, the method can comprise tracking the orbital debris target with a passive optical tracking station and transmitting a respective signal indicative of the orbit of the orbital debris target, to the receiver, and the receiver can receive signals from the passive optical tracking station and process the signal received from the passive optical tracking station into a data set pertaining to the orbit of the orbital debris target. In some embodiments, the orbital debris target tracked can be a compliant target, a cooperative target, or both. In some embodiments, the orbital debris target tracked can be a non-compliant target, an uncooperative target, or both. According to various embodiments, the method can further comprise optically tracking the orbital debris target with a passive optical tracking station based on the data sets stored in the datastore. 
         [0017]    According to various embodiments, the method can comprise also tracking a second orbital debris target using the plurality of laser ranging stations, and storing, in the datastore, data sets pertaining to the orbit of the second orbital debris target. The data sets of both the orbital debris target and the second orbital debris target can be cataloged in the datastore. Information from the cataloged data sets can be compared to positional information pertaining to a low Earth orbit asset and, if necessary, the asset can be repositioned based on the comparison, for example, to avoid a collision. 
         [0018]    According to various embodiments of the present invention, a system and method for adapting laser ranging and optical tracking capabilities on selected, optically-uncooperative (no retro reflectors) orbital debris targets in low Earth orbit (LEO). The system and method can be utilized, for example, at NASA&#39;s Goddard Space Flight Center (GSFC) in Greenbelt, Md., and more particularly at the NASA-GSFC Goddard Geophysical and Astronomical Observatory (GGAO) laser ranging facility. 
         [0019]    According to various embodiments, one or more laser ranging facilities are used in a worldwide network of sites to locate and track orbital debris. As an example, NASA&#39;s GGAO 1.2 meters (1.2 m) laser ranging facility can be used as an ODLR laboratory to develop, demonstrate, and facilitate a worldwide network of adaptive or new sites dedicated to aid the orbital debris abatement community. Although the GGAO 1.2 m laser ranging facility was built as one of the first dedicated facilities for laser ranging to man-made orbiting satellites, it has been used for a wide variety of experiments. Recently, the facility was used to provide on-orbit and in-cruise calibration for laser altimeter instruments as described in Sun et al., “Laser Ranging between the Mercury Laser Altimeter and an Earth-based Laser Satellite Tracking Station over a 24-million-km Distance,” OSA Annual Meeting, Tucson Ariz., Oct. Proceedings, (2005), which is incorporated herein in its entirety by reference. See also Smith et al., “Two-Way Laser Link over Interplanetary Distance,” Science Magazine, 311 (Jan. 6, 2006), which is incorporated herein in its entirety by reference. Such a facility can be continually updated and upgraded to keep pace with evolving tracking technology, for example, by periodic upgrades and recoating of the telescope optics. The systems and methods of the present invention do not necessarily need to compete with the current infrastructure of RF radar and passive optical tracking centers, but can add capability to the ongoing debris tracking network. For example, the present invention can incorporate sub-meter level skin tracking data products into the orbital debris database for the largest and riskiest targets. The new data products can be incorporated into the current and active database and assist in any object tracking requests by the orbital debris community. The improved resolution tracking data allows conjunction assessment predictions to be refined, reducing false reports of imminent risks. By building on decades of sub-centimeter-precision laser ranging expertise and technology advancement for the geoscience community, the present invention can provide information useful in making minor adaptations in hardware, software, and procedures and can quickly demonstrate ground based capabilities that will advance the orbital predictions of selected high-risk targets to the meter-level regime, in a short amount of time and at relatively low cost. 
       Network and Modeling 
       [0020]    The present invention provides significant improvements over current RF and passive optical tracking methods by achieving meter-level ranging precision on passive targets. Feedback from initial results can be used to determine ranging link boundary conditions in debris size and orbit altitude, and can be used to quantify system improvements that might be needed to optimize this much-needed capability. 
         [0021]    Navigation analysis can be conducted using the Orbit Determination Toolbox (ODTBX), developed and used extensively by Goddard&#39;s Navigation &amp; Mission Design Branch. Assorted initial conditions and perturbations such as Solar and Lunar effects, solar radiation pressure and atmospheric drag can all be incorporated to produce a first order prediction of a LEO object&#39;s orbit. A plurality of different SLR facilities can be used to track a single object, for example, as it orbits the Earth and/or over a period of time. For example, three representative SLR facilities such as those located in Greenbelt, Md. (GGAO), White Sands, New Mexico, and Canberra, Australia, can provide periodic tracking of a single object for a period of 24 hours. SLR measurements of the passive target are simulated and processed in a weighted batch least-squares estimator to assess orbit determination accuracy. A linear covariance analysis considering errors in the object&#39;s position, velocity, and atmospheric drag modeling can be used to show that deterministic position uncertainties at the meter-level are possible using SLR measurements. 
         [0022]    Preliminary analysis suggests that using SLR measurements yields higher precision estimates of the debris object&#39;s orbit. We know from routine sub-cm ranging accuracies to orbital cooperative targets over the last few decades that meter-level first order ranging can be achieved with relative ease using NASA&#39;s current state of operation. By optimizing the system, according to the present invention, for the higher variant properties of orbital debris, the repeatability and capability of the system can be improved likewise, and can be reproduced inexpensively around the globe. There are agreements in place at several international SLR stations with NASA that can contribute to this work. 
         [0023]    Table 1 below lists the various International Laser Ranging Service (ILRS) system locations in the global network of NASA&#39;s cooperative geophysical SLR ground station. Laser system sites can be brought online across the world, for example, one in South America, one in Europe, one in North America, and one in Japan. Mobile systems can also be used in the global network. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                 IERS 
                 IGS 
                   
                 IDS 
               
               
                   
                   
                 Location Name, 
                 CDDIS 
                 DOMES 
                 Site 
                 IVS 
                 Site 
               
               
                 Monument 
                 Code 
                 Country 
                 SOD 
                 Numbers 
                 Log 
                 Site Log 
                 Log 
               
               
                   
               
             
             
               
                 1824 
                 GLSL 
                 Golosiiv, 
                 18248101 
                 12356S001 
                 GLSV 
                 — 
                 — 
               
               
                   
                   
                 Ukraine 
               
               
                 1831 
                 LVIL 
                 Lviv, Ukraine 
                 18318501 
                 12368S001 
                 SULP 
                 — 
                 — 
               
               
                 1863 
                 MAID 
                 Maidanak 2, 
                 18635101 
                 12340S001 
                 — 
                 — 
                 — 
               
               
                   
                   
                 Uzbekistan 
               
               
                 1864 
                 MAIL 
                 Maidanak 1, 
                 18645401 
                 12340S002 
                 — 
                 — 
                 — 
               
               
                   
                   
                 Uzbekistan 
               
               
                 1868 
                 KOML 
                 Komsomolskna- 
                 18685901 
                 12341S001 
                 — 
                 — 
                 — 
               
               
                   
                   
                 Amure, 
               
               
                   
                   
                 Russia 
               
               
                 1873 
                 SIML 
                 Simeiz, Ukraine 
                 18734901 
                 12337S003 
                 CRAO 
                 CRIMEA 
                 — 
               
               
                 1874 
                 MDVS 
                 Mendeleevo 2, 
                 18748301 
                 12309S003 
                 MDVJ 
                 — 
                 — 
               
               
                   
                   
                 Russia 
               
               
                 1879 
                 ALTL 
                 Altay, Russia 
                 18799401 
                 12372S001 
                 — 
                 — 
                 — 
               
               
                 1884 
                 RIGL 
                 Riga, Latvia 
                 18844401 
                 12302S002 
                 RIGA 
                 — 
                 — 
               
               
                 1886 
                 ARKL 
                 Arkhyz, Russia 
                 18869601 
                 12373S001 
                 — 
                 — 
                 — 
               
               
                 1887 
                 BAIL 
                 Baikonur, 
                 18879701 
                 25603S001 
                 — 
                 — 
                 — 
               
               
                   
                   
                 Kazakhstan 
               
               
                 1888 
                 SVEL 
                 Svetloe, Russia 
                 18889801 
                 12350S002 
                 SVTL 
                 SVETLOE 
                 — 
               
               
                 1889 
                 ZELL 
                 Zelenchukskya, 
                 18899901 
                 12351S002 
                 ZECK 
                 ZELENCHK 
                 — 
               
               
                   
                   
                 Russia 
               
               
                 1890 
                 BADL 
                 Badary, Russia 
                 18900901 
                 12338S004 
                 BADG 
                 BADARY 
                 BADB 
               
               
                 1891 
                 IRKL 
                 Irkutsk, Russia 
                 18915301 
                 12313S007 
                 IRKJ 
                 — 
                 — 
               
               
                 1893 
                 KTZL 
                 Katzively, 
                 18931801 
                 12337S006 
                 CRAO 
                 CRIMEA 
                 — 
               
               
                   
                   
                 Ukraine 
               
               
                 7040 
                 OCTL 
                 Wrightwood, 
                 70409201 
                 49901S001 
                 — 
                 — 
                 — 
               
               
                   
                   
                 California 
               
               
                 7045 
                 APOL 
                 Apache Point, 
                 70459501 
                 49447S001 
                 — 
                 — 
                 — 
               
               
                   
                   
                 NM 
               
               
                 7080 
                 MDOL 
                 McDonald 
                 70802419 
                 40442M006 
                 MDO1 
                 FD-VLBA 
                 — 
               
               
                   
                   
                 Observatory, 
               
               
                   
                   
                 Texas 
               
               
                 7090 
                 YARL 
                 Yarragadee, 
                 70900513 
                 50107M001 
                 YAR2 
                 YARRA12M 
                 YASB 
               
               
                   
                   
                 Australia 
                   
                   
                 YAR3 
               
               
                   
                   
                   
                   
                   
                 YARR 
               
               
                 7105 
                 GODL 
                 Greenbelt, 
                 71050725 
                 40451M105 
                 GODE 
                 GGAO12 
                 GRFB 
               
               
                   
                   
                 Maryland 
                   
                   
                 GODZ 
               
               
                   
                   
                   
                   
                   
                 GODN 
               
               
                   
                   
                   
                   
                   
                 GODS 
               
               
                 7110 
                 MONL 
                 Monument 
                 71100412 
                 40497M001 
                 MONP 
                 — 
                 — 
               
               
                   
                   
                 Peak, 
               
               
                   
                   
                 California 
               
               
                 7119 
                 HA4T 
                 Haleakala, 
                 71191402 
                 40445S009 
                 MAUI 
                 — 
                 — 
               
               
                   
                   
                 Hawaii 
               
               
                 7124 
                 THTL 
                 Tahiti, French 
                 71240802 
                 92201M007 
                 FAAA 
                 — 
                 PAUB 
               
               
                   
                   
                 Polynesia 
                   
                   
                 THTI 
               
               
                   
                   
                   
                   
                   
                 THTG 
               
               
                   
                   
                   
                   
                   
                 TAH1 
               
               
                   
                   
                   
                   
                   
                 TAH2 
               
               
                 7231 
                 WUHL 
                 Wuhan, China 
                 72312901 
                 21602S004 
                 WUHN 
                 — 
                 JIUB 
               
               
                 7237 
                 CHAL 
                 Changchun, 
                 72371901 
                 21611S001 
                 CHAN 
                 — 
                 — 
               
               
                   
                   
                 China 
               
               
                 7249 
                 BEIL 
                 Beijing, China 
                 72496102 
                 21601S004 
                 BJFS 
                 — 
                 — 
               
               
                 7308 
                 KOGC 
                 Koganei, Japan 
                 73085001 
                 21704S002 
                 KGNI 
                 KOGANEI 
                 — 
               
               
                   
                   
                 (CRL) 
               
               
                 7358 
                 GMSL 
                 Tanegashima, 
                 73588901 
                 21749M001 
                 GMSD 
                 — 
                 — 
               
               
                   
                   
                 Japan 
               
               
                 7359 
                 DAEK 
                 Daedeok, 
                 73592601 
                 23902S002 
                 DAEJ 
                 — 
                 — 
               
               
                   
                   
                 Republic of 
               
               
                   
                   
                 Korea 
               
               
                 7403 
                 AREL 
                 Arequipa, Peru 
                 74031306 
                 42202M003 
                 AREG 
                 — 
                 ARFB 
               
               
                   
                   
                   
                   
                   
                 AREQ 
               
               
                   
                   
                   
                   
                   
                 AREV 
               
               
                 7405 
                 CONL 
                 Concepcion, 
                 74057904 
                 41719M001 
                 CONZ 
                 TIGOCONC 
                 — 
               
               
                   
                   
                 Chile 
                   
                   
                 CONT 
               
               
                 7406 
                 SJUL 
                 San Juan, 
                 74068801 
                 41508S003 
                 — 
                 — 
                 — 
               
               
                   
                   
                 Argentina 
               
               
                 7407 
                 BRAL 
                 Brasilia, Brazil 
                 74072701 
                 48081S001 
                 — 
                 — 
                 — 
               
               
                 7501 
                 HARL 
                 Hartebeesthoe, 
                 75010602 
                 30302M003 
                 HARB 
                 HARTRAO 
                 HRMB 
               
               
                   
                   
                 South Africa 
                   
                   
                 HRAO 
                 HART15M 
               
               
                 7806 
                 METL 
                 Metsahovi, 
                 78067601 
                 10503S014 
                 METS 
                 tbd 
                 MEUB 
               
               
                   
                   
                 Finland 
               
               
                 7810 
                 ZIML 
                 Zimmerwald, 
                 78106801 
                 14001S007 
                 ZIMM 
                 — 
                 — 
               
               
                   
                   
                 Switzerland 
                   
                   
                 ZIM2 
               
               
                   
                   
                   
                   
                   
                 ZIMJ 
               
               
                 7811 
                 BORL 
                 Borowiec, 
                 78113802 
                 12205S001 
                 BOR1 
                 — 
                 — 
               
               
                   
                   
                 Poland 
               
               
                 7820 
                 KUNL 
                 Kunming, China 
                 78208201 
                 21609S002 
                 KUNM 
                 KUNMING 
                 — 
               
               
                 7821 
                 SHA2 
                 Shanghai, China 
                 78212801 
                 21605S010 
                 SHAO 
                 SESHAN25 
                 — 
               
               
                 7824 
                 SFEL 
                 San Fernando, 
                 78244502 
                 13402S007 
                 SFER 
                 — 
                 — 
               
               
                   
                   
                 Spain 
                   
                   
                 ROAP 
               
               
                 7825 
                 STL3 
                 Mt Stromlo, 
                 78259001 
                 50119S003 
                 STR1 
                 — 
                 MSPB 
               
               
                   
                   
                 Australia 
                   
                   
                 STR2 
               
               
                 7827 
                 SOSW 
                 Wettzell, 
                 78272201 
                 14201S045 
                 WTZR 
                 WETTZELL 
                 — 
               
               
                   
                   
                 Germany 
                   
                   
                 WTZS 
                 WETTZ13N 
               
               
                   
                   
                   
                   
                   
                 WTZA 
               
               
                   
                   
                   
                   
                   
                 WTZZ 
               
               
                 7831 
                 HLWL 
                 Helwan, Egypt 
                 78314601 
                 30101S001 
                 — 
                 — 
                 — 
               
               
                 7832 
                 RIYL 
                 Riyadh, Saudi 
                 78325501 
                 20101S001 
                 SOLA 
                 — 
                 — 
               
               
                   
                   
                 Arabia 
               
               
                 7838 
                 SISL 
                 Simosato, Japan 
                 78383603 
                 21726S001 
                 SMST 
                 — 
                 — 
               
               
                 7839 
                 GRZL 
                 Graz, Austria 
                 78393402 
                 11001S002 
                 GRAZ 
                 — 
                 — 
               
               
                 7840 
                 HERL 
                 Herstmonceu, 
                 78403501 
                 13212S001 
                 HERS 
               
               
                   
                   
                 United Kingdom 
                   
                   
                 HERT 
               
               
                 7841 
                 POT3 
                 Potsdam, 
                 78418701 
                 14106S011 
                 POT3 
                 — 
                 — 
               
               
                   
                   
                 Germany 
               
               
                 7845 
                 GRSM 
                 Grasse, France 
                 78457801 
                 10002S002 
                 GRAS 
                 — 
                 GRAB 
               
               
                   
                   
                 (LLR) 
                   
                   
                 GRAC 
               
               
                 7941 
                 MATM 
                 Matera, Italy 
                 79417701 
                 12734S008 
                 MATE 
                 MATERA 
                 — 
               
               
                   
                   
                 (MLRO) 
                   
                   
                 MAT1 
               
               
                 8834 
                 WETL 
                 Wettzell, 
                 88341001 
                 14201S018 
                 WTZR 
                 WETTZELL 
                 — 
               
               
                   
                   
                 Germany 
                   
                   
                 WTZS 
                 WETTZ13N 
               
               
                   
                   
                 (WLRS) 
                   
                   
                 WTZA 
               
               
                   
                   
                   
                   
                   
                 WTZZ 
               
               
                   
               
             
          
         
       
     
       Facility and Operations 
       [0024]    According to various embodiments, the GGAOs 1.2 m telescope laser ranging station can be used to achieve meter-level range accuracy on cooperative satellite targets as well as large, uncooperative debris targets. Many newly launched assets incorporate externally mounted, Earth-facing retro reflectors so ground based laser ranging installations can use them as cooperative targets. These retro reflectors greatly increase the effective laser link margin and create numerous opportunities for orbital refinement throughout a mission as well as aiding the geodetic community. In 2005, NASA used the system to achieve and active optical link with the Messenger spacecraft, as it was on its way to Mercury. The Mercury Laser Altimeter (MLA) instrument was aimed at Earth and the 1.2 m telescope configured to track Messenger. Each system engaged its laser lidar/ranging systems and is able to achieve an active optical link between the two instruments on multiple occasions. This 24×10 6  km link allowed the Messenger team to perform unique in-situ operational calibration and tests with its altimeter system, otherwise not possible prior to reaching its planetary destination. This feat fully demonstrates the facilities ability to track and bore site to difficult, unique targets of opportunity, and achieve few photon level waveform capture in a relatively high light pollution environment. 
         [0025]    According to various embodiments of the present invention, ODLR can serve as an experimental baseline for developing an optimized system for laser ranging to smaller, noncompliant (skin tracking) targets. According to various embodiments, methods can focus on continuing efforts to identify and track large uncooperative orbital debris (without retro-reflectors). Laser and detector hardware can be optimized for locating and tracking smaller (about 10 cm) debris targets. According to various embodiments, GGAO can utilize NASA&#39;s in-house SLR expertise and its membership in the ILRS with active stations worldwide, as shown in Table 1 above, to offer a unique opportunity to rapidly adapt high resolution SLR techniques to address the growing orbital debris problem. 
         [0026]    According to various embodiments, SLR techniques can be employed at GGAO to find new debris, improve tracking of known debris, and measure tumble rates on larger objects. In some embodiments, the illumination of a specific target by an SLR system for optical tracking can be used by a spacecraft as a target to characterize diffuse reflection of directed laser energy from the SLR system, of a known passive target, which can be optically tracked by another station. This added capability enables multiple optical sites to passively track illuminated targets for further enhancement of orbital predictions, further adding to the orbital database without the necessity of having high precision laser ranging capability at every station of the network. 
       ODLR Detection and Tracking Methods 
       [0027]    The current conjunction assessment process of predicting the probability of collision is often insufficient to provide truly “actionable” information for maneuver decisions. Calculating the probability of collision involves estimating and propagating the state and covariance of both the spacecraft and the debris object. As the uncertainty in the debris object&#39;s state increases, so does the false alarm and missed detection rate. As a result, hypothetically the next on-orbit collision may have been predicted, but with insufficient precision to justify an avoidance maneuver. 
         [0028]    The more accurate (and conversely, with lower variance) estimate of the debris object orbit leads to more precise calculation of the probability of collision with greater confidence. As a result, “false detections” (where collision avoidance maneuvers are preformed unnecessarily) occur less frequently, reducing operational complexity and cost. Also, better estimates of collision probabilities also reduce the risk of a missed detection, potentially preventing a collision. SLR, according to the present invention, thus enables the conjunction analysis end-user to receive fewer collision warnings, with higher confidence levels, and more actionable information. 
         [0029]    High-accuracy tracking data, achievable with ODLR according to the present invention, significantly improves existing prediction models for these highly random and changing targets. Improving these models provides more time for spacecraft to avoid potential impacts and reduces the significant number of expensive and time-consuming maneuvers executed due to false alarms. Improving the debris object&#39;s orbit estimate results in a more accurate probability of collision calculation. According to various embodiments of the present invention, the inclusion of SLR techniques into the current RADAR debris grid, models, and current SLR operations to friendly targets, the absolute range accuracy improves by 10× or more depending on target size, albedo, orbit, and shape. Thus, the inclusion of this active orbital range measurement technology can also be used to improve the orbital estimates of 48-72 hour conjunction predictions. 
       ODLR Network Operation 
       [0030]    As of 2015, the GSFC Flight Dynamics Facility (FDF) was providing Conjunction Assessment Risk Mitigation support for more than 80 NASA missions. The JSpOC provides close approach predictions data to the NASA Robotic Conjunction Assessment Risk Analysis (CARA) Team, also at GSFC. The CARA team analyzes the JSpOC data, and performs a risk analysis to quantify threats. The CARA team provides risk assessment analysis results and trends to the Mission Flight and Operations Teams and makes recommendations, if required, to Mission Operations Teams concerning maneuver avoidance planning. While the CARA process provides important risk assessments, any close approach prediction requires significant analysis and quick turnaround work to disprove, and requires several meetings with the mission team to describe risk and build confidence that it is just a false alarm. Thus, the reduction in false predictions, risk analysis time and cost, provided by the ODLR laboratory provides additional benefits to both GSFC FDF and JSpOC. 
         [0031]    The Joint Space Operations Center is currently upgrading the JSpOC Mission System (JMS) that will deliver an integrated Command and Control (C 2 ) and Space Situational Awareness (SSA) capability to Joint Functional Component Command (JFCC) Space. The Service-Oriented Architecture (SOA) infrastructure enables interoperability and adaptability with the non-Department of Defense community, including NASA. The Ground-Based Laser Ranging at NASA-GSFC for Identification and Tracking of Orbital Debris system data and flight dynamics products can be integrated into their External Space and Other Support Services part of the overall JMS. 
         [0032]    A dedicated ODLR laboratory can provide an important baseline analysis capability for evolving orbital debris characteristics that can define and drive requirements for orbital debris removal design concepts. The analysis can facilitate the validation of current and future designs and concepts. 
         [0033]    GGAO&#39;s 1.2 m facility can be adapted for ODLR operations with meter-level and finer tracking accuracies to uncooperative large targets and to smaller sub-meter targets. Based on initial demonstration tracks, data can be incorporated into a model and link margin calculations to produce a to-do list of remaining upgrades and operations enhancements to produce the highest level of accuracy possible, and to link to the smallest target possible, at least on a case-to-case confirmation basis. Other international SLR sites, in cooperation with Goddards GGAO, can be adapted to periodically track LEO debris, and improve the multi-site advantages toward solving this problem. Dedicated ODLR sites can be installed worldwide with near real-time orbital and tracking data feeding into the JSpOC and SSA databases, for example, at sister ILRS stations in Australia, France, and Austria. NASA&#39;s involvement can provide the critical mass needed to enable a global network of dedicated ODLR sites for debris tracking and aid in abatement processes. The laser-based tracking of orbital debris provides another layer of detection and protection of valuable space assets, currently not available through any other, readily active means. 
         [0034]    Each of the following references is incorporated herein in its entirety by reference: 
         [0035]    [1] NASA Orbital Debris Program Office, “Orbital Debris Frequently Asked Questions”, March (2012). http ://www.orbitaldebris.jsc.nasa.gov/faqs.html#3. 
         [0036]    [2] McKie, Robin and Day, Michael “Warning of catastrophe from mass of ‘space junk’” The Observer, 24 Feb. (2008). 
         [0037]    [3] McGarry, J. Zagwodzki, T. and Degnan, J. J., “Large aperture high accuracy satellite laser tracking,” SPIE 641, 77-83, (1986). 
         [0038]    [4] Pearlman, et al, “NASA&#39;s Next Generation Space Geodesy Program,” http://space-geodesy.nasa.gov/docs/2012/sgp_aogs_120813.pdf, (2012). 
         [0039]    [5] International Technical Laser Workshop, “Satellite, Lunar and Planetary Laser Ranging: characterizing the space segment”, (2012). http://www.lnf.infn.it/conference/laser2012/ 
         [0040]    [6] David E. Smith, Maria T. Zuber, Xiaoli Sun, Gregory A. Neumann, John F. Cavanaugh, Jan F. McGarry, Thomas W. Zagwodzki, “Two-way laser link over interplanetary distance”, Science, 311, 53, (2006). 
         [0041]    [7] Pearlman, M. R., Degnan, J. J., and Bosworth, J. M., “The International Laser Ranging Service”, Advances in Space Research, Vol. 30, No. 2, pp. 135-143, July 2002, DOI:10.1016/50273 -1177(02)00277-6. 
         [0042]    [8] Courde, Clement, “Laser ranging on space debris with the MeO station”, OCA, France, Proc. International Technical Laser Workshop 2012, Frascati, Italy, (2012). 
         [0043]    [9] Georg, Kirchner, “Laser tracking of space debris at SLR Graz”, Austrian Academy of Sciences, Austria, Proc. International Technical Laser Workshop 2012, Frascati, Italy, (2012). 
         [0044]    [10] Smith, Craig, et al. “LASER TRACKING OF SPACE DEBRIS FOR PRECISION ORBIT DETERMINATION.” Advances in the Astronautical Sciences 142 (2011). 
         [0045]    [11] NASA Robotic Conjunction Assessment Risk Analysis (CARA) Effort: Background and Overview, Lauri Newman, Romae Young Jan. 19, (2010). 
         [0046]    The present invention includes the following numbered aspects, embodiments, and features, in any order and/or in any combination: 
         [0047]    1. A system of laser ranging tracking facilities for tracking an orbital debris target in low Earth orbit, the system comprising: 
         [0048]    a plurality of laser ranging stations comprising at least two ground-based laser ranging stations separated from one another by at least 100 miles, each laser ranging station comprising a transmitter for transmitting a respective signal indicative of the orbit of the orbital debris target; 
         [0049]    a receiver configured to receive the signals from the laser ranging stations; 
         [0050]    a processor configured to process the signals received by the receiver into data sets each pertaining to the orbit of the orbital debris target; and 
         [0051]    a datastore configured to store the data sets pertaining to the orbit of the orbital debris target, wherein at least one of the ground-based laser ranging stations comprises a high power laser configured to provide laser pulses at a wavelength of from 1.4 μm to 1.9 μm at a pulse energy of 100 mJ or greater and at a repetition rate of from 10 Hz to 100 Hz. 
         [0052]    2. The system of any preceding or following embodiment/feature/aspect, wherein the processor is further configured to: 
         [0053]    process the data sets into orbital data pertaining to the orbit of the orbital debris target; 
         [0054]    store the orbital data in the datastore; and 
         [0055]    calculate a future orbit path of the orbital debris target based on the stored orbital data. 
         [0056]    3. The system of any preceding or following embodiment/feature/aspect, wherein the high power laser is configured to provide pulsed laser light at a wavelength of about 1.5 μm. 
         [0057]    4. The system of claim  1 , further comprising at least one laser ranging satellite configured to laser range the orbital debris target and transmit a signal to the receiver indicative of the orbit of the orbital debris target. 
         [0058]    5. The system of any preceding or following embodiment/feature/aspect, wherein the laser ranging satellite comprises a high power laser configured to provide laser pulses at a wavelength from 1.0 μm to 1.9 μm at a pulse energy of 100 mJ or greater and at a repetition rate of from 10 Hz to 100 Hz. 
         [0059]    6. The system of any preceding or following embodiment/feature/aspect, wherein the high power laser of the laser ranging satellite is configured to provide pulsed laser light at a wavelength of about 1.5 μm. 
         [0060]    7. The system of any preceding or following embodiment/feature/aspect, further comprising a radio frequency radar station configured to track the orbital debris target and transmit a respective signal indicative of the orbit of the orbital debris target, to the receiver, wherein the receiver is further configured to receive signals from the radio frequency radar station. 
         [0061]    8. The system of any preceding or following embodiment/feature/aspect, further comprising a passive optical tracking radar station configured to track the orbital debris target and transmit a respective signal indicative of the orbit of the orbital debris target, to the receiver, wherein the receiver is further configured to receive signals from the passive optical tracking radar station. 
         [0062]    9. A method tracking an orbital debris target in low Earth orbit, the method comprising: laser ranging the orbital debris target using a plurality of laser ranging stations comprising at least two ground-based laser ranging stations, the at least two ground-based laser ranging stations being separated from one another by at least 100 miles; 
         [0063]    transmitting a respective signal from each of the laser ranging stations indicative of the orbit of the orbital debris target; 
         [0064]    receiving at a receiver the transmitted signals from the laser ranging stations; 
         [0065]    processing the signals received by the receiver into data sets each pertaining to the orbit of the orbital debris target; and 
         [0066]    storing in a datastore the data sets pertaining to the orbit of the orbital debris target, 
         [0067]    wherein at least one of the ground-based laser ranging stations laser ranges with a high power laser that provides laser pulses at a wavelength of from 1.4 μm to 1.9 μm at a pulse energy of 100 mJ or greater and at a repetition rate of from 10 Hz to 100 Hz. 
         [0068]    10. The method of any preceding or following embodiment/feature/aspect, wherein the processor: 
         [0069]    processes the data sets into orbital data pertaining to the orbit of the orbital debris target; 
         [0070]    stores the orbital data in the datastore; and 
         [0071]    calculates a future orbit path of the orbital debris target based on the stored orbital data. 
         [0072]    11. The method of any preceding or following embodiment/feature/aspect, wherein the high power laser provides pulsed laser light at a wavelength of about 1.5 μm. 
         [0073]    12. The method of any preceding or following embodiment/feature/aspect, further comprising laser ranging the orbital debris target with at least one laser ranging satellite and transmitting a satellite signal from the laser ranging satellite to the receiver, the satellite signal being indicative of the orbit of the orbital debris target, wherein the receiver receives the satellite signal and the processing further comprises processing the satellite signal into a data set pertaining to the orbit of the orbital debris target. 
         [0074]    13. The method of any preceding or following embodiment/feature/aspect, wherein the laser ranging satellite produces high power laser pulses at a wavelength from 1.0 μm to 1.9 μm at a pulse energy of 100 mJ or greater and at a repetition rate of from 10 Hz to 100 Hz. 
         [0075]    14. The method of any preceding or following embodiment/feature/aspect, wherein the high power laser of the laser ranging satellite produces pulsed laser light at a wavelength of about 1.5 μm. 
         [0076]    15. The method of any preceding or following embodiment/feature/aspect, further comprising tracking the orbital debris target with a radio frequency radar station and transmitting a respective signal indicative of the orbit of the orbital debris target, to the receiver, wherein the receiver receives signals from the radio frequency radar station and the processing further comprises processing the signal received from the radio frequency radar station into a data set pertaining to the orbit of the orbital debris target. 
         [0077]    16. The method of any preceding or following embodiment/feature/aspect, further comprising tracking the orbital debris target with a passive optical tracking station and transmitting a respective signal indicative of the orbit of the orbital debris target, to the receiver, wherein the receiver receives signals from the passive optical tracking station and the processing further comprises processing the signal received from the passive optical tracking station into a data set pertaining to the orbit of the orbital debris target. 
         [0078]    17. The method of any preceding or following embodiment/feature/aspect, wherein the orbital debris target is a non-compliant target, an uncooperative target, or both. 
         [0079]    18. The method of any preceding or following embodiment/feature/aspect, further comprising optically tracking the orbital debris target with a passive optical tracking station based on the data sets stored in the datastore. 
         [0080]    19. The method of any preceding or following embodiment/feature/aspect, further comprising: 
         [0081]    tracking a second orbital debris target using the plurality of laser ranging stations; 
         [0082]    storing in the datastore data sets pertaining to the orbit of the second orbital debris target; and 
         [0083]    cataloging in the datastore the data sets of both the orbital debris target and the second orbital debris target. 
         [0084]    20. The method of any preceding or following embodiment/feature/aspect, further comprising comparing information from the cataloged data sets to positional information pertaining to a low Earth orbit asset and repositioning the asset based on the comparison. 
         [0085]    The present invention can include any combination of these various features or embodiments above and/or below as set-forth in sentences and/or paragraphs. Any combination of disclosed features herein is considered part of the present invention and no limitation is intended with respect to combinable features. 
         [0086]    The entire contents of all references cited in this disclosure are incorporated herein in their entireties, by reference. Further, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether such ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range. 
         [0087]    Herein the term “about” is intended to encompass a deviation of from plus 5% to minus 5% of the value modified. So, for example, by “about 1.5 μm,” what is meant is from 1.425 μm to 1.575 μm. 
         [0088]    Other embodiments of the present invention will be apparent to those skilled in the art from consideration of the present specification and practice of the present invention disclosed herein. It is intended that the present specification and examples be considered as exemplary only with a true scope and spirit of the invention being indicated by the following claims and equivalents thereof.