US 20130006449Al (19) United States (12) Patent Application Publication (10) Pub. No.: US 2013/0006449 A1 Hindman (43) Pub. Date: Jan. 3, 2013

(54) APPARATUS, SYSTEM AND METHOD FOR (52) U.S.Cl...... 701/13;356/614 SPACECRAFT NAVIGATION USING EXTRASOLAR PLANETARY SYSTEMS (57) ABSTRACT (76) Inventor: George William Hindman, Austin, TX (Us) (21) Appl. No.: 13/538,655 The present invention provides an innovative apparatus, sys tem and method for onboard spacecraft location determina (22) Filed: Jun. 29, 2012 tion and navigation by employing the observation of extraso Related US. Application Data lar planetary system motion. In one apparatus embodiment a gas absorption cell is placed between a sensor (60) Provisional application No. 61/571,554, ?led on Jun. and the light from a reference star system With at least one 30, 2011. , such that the sensor can detect the spectrum Publication Classi?cation through the gas absorption cell. Radial velocities can be cal culated via Doppler Spectroscopy techniques and incorpo (51) Int. Cl. rated into a spacecraft navigation solution. The present inven G01B 11/14 (2006.01) tion can enable and enhance signi?cant mission capabilities B64G 1/36 (2006.01) for future manned and unmanned space vehicles and mis G01C 21/24 (2006.01) s1ons.

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APPARATUS, SYSTEM AND METHOD FOR accurate state estimation and a realistic state error covariance. SPACECRAFT NAVIGATION USING GEONS incorporates the information from all past measure EXTRASOLAR PLANETARY SYSTEMS ments, carefully balanced With its knoWledge of the physical models governing these measurements, to produce an optimal CROSS REFERENCE TO RELATED estimate of a spacecraft’s orbit. GEONS’ high-?delity state APPLICATION dynamics model reduces sensitivity to measurement errors [0001] This application claims the bene?t of priority under and provides high-accuracy velocity estimates, permitting accurate state prediction. 35 USC §119 to US. Provisional Patent Application No. 61/571,554 ?led Jun. 30, 2011, the entire contents of Which [0009] Interplanetary missions typically employ tracking are hereby expressly incorporated by reference for all pur services from NASA’s DSN, Which provides radiometric ranging, Doppler and plane-of-sky angle measurements. For poses. spacecraft ranging, a signal is sent from one of the DSN BACKGROUND OF THE INVENTION stations on Earth to the spacecraft, Which in turn sends a signal back to Earth. The round trip transit time is measured to [0002] 1. Field of the Invention determine the line of sight slant range. TWo-Way Doppler [0003] The present invention is an innovative apparatus, tracking also uses a signal sent to and from a spacecraft; by system and method for spacecraft navigation employing the looking at the small changes in frequency, the spacecraft use of extrasolar planetary system motion. Spacecraft navi velocity along the line of sight can be determined. gation can generally be described as, but not limited to, the [0010] In general, angular measurements can be made determination of a spacecraft’s position, velocity and attitude using multiple DSN ground stations that receive spacecraft at certain times as Well as the determination of orbital param transmissions simultaneously during overlapping vieWing eters and trajectories. Extrasolar planetary systems are star periods. An additional method used by DSN is delta differ systems other than the that have planetary companions. ential one-Way range (ADOR). This is a Very Large Baseline The present invention relates to several different ?elds includ Interferometry (VLBI) technique that uses tWo ground sta ing spacecraft hardWare, softWare, navigation, astronomy, tions to simultaneously vieW a spacecraft and then a knoWn Doppler spectroscopy methods and astrometric techniques. radio source (such as a quasar) to provide an angular position [0004] 2. Description of the Related Art determination. [0005] Precise determination of spacecraft position and [0011] Unfortunately, DSN resources are limited and its velocity is necessary in order to achieve mission success for accuracies degrade over large distances. Onboard spacecraft operations of near Earth and interplanetary missions. navigation systems that can reduce tracking requirements for Onboard ?ight technologies can provide spacecraft position, the DSN are currently needed. Furthermore, GPS satellites navigation and timing (PNT). Areas of related art include orbiting the Earth are of limited use for deep space missions. traditional spacecraft navigation hardWare and softWare, Thus, hardWare and softWare systems and methods that pro tracking such as NASA’s Deep Space Network (DSN), the vide precise navigation solutions using a methodology that is Global Positioning System (GPS), X-ray navigation and independent of Earth based systems are not only innovative extrasolar planetary detection. and novel but are currently needed for spacecraft navigation. [0006] Space navigation traditionally relies on initial [0012] Some recent research and development With spacecraft position, velocity and attitude estimates that are autonomous deep space navigation has examined the use of regularly updated by onboard inertial measurement unit pulsed X-ray radiation emitted by pulsars. Such investiga (IMU) data. An IMU is a device that measures a spacecraft’s tions designate X-ray millisecond pulsars as a potential signal velocity changes and orientation using a combination of source to be observed by a spacecraft. HoWever, the speci?c accelerometers and gyroscopes. Spacecraft orientation can characteristics of pulsars are limiting and very different from also be aided by a star tracker, Which is an optical device that main sequence such as our sun. The current invention measures the relative position(s) of star(s) against the celes uses the properties of main sequence stars and their associ tial background using photocells or a charged couple device ated extrasolar planets. (CCD) camera. Additional components such as horizon or [0013] In the past 15 or so, over 700 extrasolarplanets sun sensors are also traditionally employed. (or ) have been discovered orbiting around 560 [0007] Methods of onboard orbit and position determina main sequence stars (some stars have multiple detected tion involve accurate updates to the spacecraft’s navigation exoplanets). These stars are evenly distributed throughout the state matrix (“Nay State”). Periodic updates from external celestial sphere and most are Within several hundred light signals can be processed by onboard softWare algorithms and years (ly) of Earth. Some potential exoplanet reference stars ?lters. As an example, in loW Earth orbit (LEO), the Nay State include, but are not limited to, (10 ly aWay), can be re?ned by employing Kalman ?ltering and data from Gliese 86 (36 ly), 47 Ursae Majoris (43 ly), 55 Cancri (44 ly), terrestrial navigation aids such as C band radar tracking or the Upsilon Andromedae (44 ly), 51 Pegasi (48 ly) and Tau Boo GPS. There are various Ways to implement these softWare tis (49 ly). All have Well knoWn characteristics and are even ?ltering capabilities, one of Which is NASA’s GPS Enhanced visible to the naked eye. Onboard Navigation SoftWare (GEONS). [0014] Before the discovery of exoplanets, the only planets [0008] GEONS supports the acceptance of many one Way knoWn to exist Were those in our oWn solar system. The forWard Doppler, optical sensor observation and accelerom motion of the Earth about our Sun is Well understood and the eter data types. GEONS Was designed for autonomous opera Whole solar system in fact rotates around a common center of tion Within the limited resources of an onboard computer. It , knoWn as the barycenter. Astronomers, in order to employs an extended Kalman ?lter (EKF) augmented With detect possible planets around stars other than our Sun, had to physically representative models for gravity, atmospheric separate knoWn and unknoWn stellar motion to determine the drag, solar radiation pressure, clock bias and drift to provide motion of other stars about their oWn barycenters. The initial US 2013/0006449 A1 Jan. 3, 2013

theory postulated that if exoplanets did exist, their orbits DETAILED DESCRIPTION OF THE PREFERRED Would cause their parent star to Wobble by a small amount. EMBODIMENT This motion Was indeed detected, yielding numerous [0025] Nay State determination through the use of extraso exoplanet discoveries. The measurements to date have pro lar planetary system motion data is an innovative method for duced noW Well knoWn patterns of highly stable, predictable onboard spacecraft navigation. It Will signi?cantly enable and exoplanetary system stellar motion With respect to our oWn enhance mission capabilities for future manned and solar barycenter. This exoplanetary system stellar motion can unmanned space vehicles as Well as reducing the need for be used to determine the location of a spacecraft both Within Deep Space Navigation resources. Over 700 extrasolar plan and outside of our solar system. This is the methodology employed by the present invention. ets have been discovered around nearby main sequence stars Within the past 15 years. The motion of these extrasolar plan ets around their stellar barycenters provides a stable, highly SUMMARY OF THE INVENTION predictable natural signal pattern. Observations from these [0015] The present invention is an apparatus, system and star systems alloW for enhanced spacecraft self determination method for spacecraft location determination and navigation of orbits and position as Well as navigation. employing extrasolar planetary system motion. The appara tus, system and method provide onboard orbit or location Extrasolar Planetary System Motion and determination and navigation capabilities during spacecraft Measurements operations through the use of specialiZed reference stars that [0026] Earth based exoplanet searches have sought to iden have exoplanet companions. The motion of these exoplanets tify planetary systems by observing characteristics of the around the reference star’s barycenter provides a stable, parent star about Which the potential planet is orbiting. The highly predictable natural signal pattern. The measurements main methodologies employed for such exoplanet detection of these signal patterns are taken onboard the spacecraft and have been and Doppler spectroscopy. In celestial are used With onboard softWare algorithm estimation tech mechanics, the simplest case is of a single planet orbiting niques to determine both spacecraft location and navigation. around one star. The system orbital parameters can be derived The present invention enables and enhances signi?cant mis from Equation 1: sion capabilities for future manned and unmanned space vehicles as Well as reducing DSN tracking requirements and resources. Where the (M*, mp) are in solar units, the semi-major [0016] The present invention can provide primary or sec axis (a) is in astronomical units (AU) and the period (P) is in ondary navigation capabilities for space missions. It is years. The motion of the star is much smaller than that of the expected to provide positional solutions anyWhere Within the associated planet. Using techniques for indirect observation solar system as Well as beyond our solar system. Primary of exoplanets, the small motion of the reference star is autonomous navigation can be incorporated into spacecraft detected, alloWing for calculations that infer the existence of designed for geostationary, elliptical high earth orbits, or the exoplanet. deep space orbits or trajectories. Back-up or secondary navi [0027] Astrometry attempts to measure the movement of a gation capabilities could be available for emergency situa star With respect to background stars. In cases Where the tions in loW and medium Earth orbits When primary naviga movement is apparent, parallax is being measured. If a star tion is lost (such as in the case ofdenied access to GPS). The Were seen to have an elliptical motion, the probable explana present invention could be used for manned missions and tion Would be that the Wobble is due to a star orbiting about its Would be particularly useful at locations currently of interest barycenter. Using Equation 1 and the fact that the semi-major such as lunar orbits, asteroids, comets, libration points, Mar axis can be measured as an angle, 6, yields Equation 2: tian moons or outer solar system planets.

BRIEF DESCRIPTION OF THE DRAWINGS mp 51 mp( P )2/3 (2) [0017] A better understanding of the present invention can be obtained When the folloWing detailed description of the preferred embodiment is considered in conjunction With the Where 6 is in arcsec When a is in AU, both masses are in solar folloWing draWings, in Which: units, distance (r) is in (pc) and P is in years. For [0018] FIG. 1 illustrates Solar motion about the barycenter, example, if one Were to vieW our solar system from a distance from the time period of 1960 to 2025 AD. of 10 pc, Jupiter Would appear as an 11.9 disturbance in [0019] FIG. 2 illustrates the of the Sun as it the Sun’s motion With a 0.5 milliarcsec amplitude. FIG. 1 orbits the solar system barycenter. displays What our solar system motion about its barycenter Would look like if vieWed from the north ecliptic pole at a [0020] FIG. 3 illustrates a spacecraft in the space environ distance of 10 pc, With the right horiZontal axis pointing to the ment. Vernal Equinox. Planet detection is mo st sensitive to stars that [0021] FIG. 4 illustrates a functional spacecraft block dia are near the solar neighborhood and have a large planet. Mo st gram. of the exoplanets detected to date have been described as [0022] FIG. 5 illustrates the components of a standard star “large Jupiters”, With periods measured in days. tracker. [0028] For astrometry, the motion of the star is most pro [0023] FIG. 6 illustrates an exoplanetary star tracker appa nounced When the exoplanet(s) orbiting the star are in a plane ratus and gas absorption cell block diagram. perpendicular to the line of sight of the observationpoint. Any [0024] FIG. 7 illustrates the principle elements of an astro other orientation Would produce some cyclical motion metric interferometer. toWards and then aWay from the observation point. Doppler US 2013/0006449 A1 Jan. 3, 2013

spectroscopy takes advantage of this radial motion by trying Where (I) is the measured carrier phase, N is the phase ambi to detect the alternating red and blue spectrum shifts that a star guity integer or “integer ambiguity”, A6 is the clock bias, 7» in this orientation Would have. This Doppler motion Would and f are the GPS carrier phase Wavelength and frequency, create a variable radial velocity as dictated by Equation 3: and p is the range. Substituting fIc/K and expressing Equa tion 5 as a mathematical model yields Equation 6 and Equa tion 7: _30 mpsini _30 mp sini (3)

Where i and j are tWo points in a designated reference frame at an (t) and: Where v is in km/sec, the masses are in solar units, a is in AU, P is in years and i is the inclination of the orbit to the plane of the sky. Using the previous example for astrometry, Jupiter has a velocity variation of 13.0 msec over a period of 11.9 [0033] While the above equations are usually applied to years. Most exoplanets detected to date have larger velocity GPS and its geocentric reference frame, the same concepts variations than Jupiter, over a period of just days. FIG. 2 are employed for the space environment for the purposes of depicts the apparent radial velocity shift of our Sun, primarily this invention. The Wavelength selected could be any one of due to Jupiter, as vieWed from the Vernal Equinox for the many that are associated With the stellar signature of an extra same time period as shoWn in FIG. 1. solar planetary system and the coordinates can be in an iner tial solar reference frame tied to the solar barycenter. Using [0029] Doppler spectroscopy measurements are thus exceptionally useful, since identi?ed stars With planetary this type of solar reference frame and an appropriate timing companions have a stable, knoWn repeatable pattern of model de?ned at a speci?c location, information observed at motion. Astrometric measurements of parallax and stellar a spacecraft can be matched With data in an onboard extraso angular displacements also provide valuable data. Since these lar planetary system database to provide a navigation solu tion. stellar motions about the barycenter are knoWn With a high degree of precision and consistently and reliably repeat over [0034] Furthermore, onboard softWare algorithms may many cycles and years, they make excellent reference employ differencing techniques for one or more extrasolar sources. Currently there are over 500 observed exoplanet star planetary systems to remove errors. A single difference cal systems. This population alloWs for a viable extrasolar plan culation could be done betWeen the measured spacecraft etary system reference database for onboard spacecraft navi Wavelength phase arrival and the phase predicted at a model gation. location. A double difference could be obtained by subtract [0030] Full three dimensional absolute and relative naviga ing tWo single differences from tWo different sources. A triple tion solutions are achievable from extrasolar planetary sys difference could be calculated by subtracting tWo double tem sources, including position and velocity determination as differences from tWo separate time epochs. Well as spacecraft attitude determination. Spacecraft naviga [0035] It is also noted that the observed star radiates in the tion algorithms and softWare ?ltering can combine onboard entire electromagnetic spectrum, so multiple Wavelengths measurements With exoplanetary stellar motion based models can be monitored at the same time. This Would provide for and other characteristics, such as source , right naturally occurring multiple frequencies from the source, ascension and to yield a solution. Absolute similar to GPS satellites broadcasting more than just one L position or delta updates to a position can be calculated and band frequency. blended With a spacecraft’s Nay State. [0031] Absolute positions may be obtained either by range Exoplanetary System Star Tracker Apparatus for or Wavelength phase measurements. In general, a spacecraft Space Navigation range (p) can be calculated from the difference in the transmit [0036] FIG. 3 depicts a partial representation of the space and receive times of one source spectrum by Equation 4: environment, With the Earth 1 orbiting the Sun 2.A spacecraft Pally-1,) (4) 3 is also depicted, With the disclosed inventions located onboard. An inertial solar reference frame 4 is shoWn With the Where c is the speed of light. If the range measurement is origin located at the solar system barycenter. The distances to knoWn as Well as the unit vector for the extrasolar planetary the Earth, Sun and spacecraft in the reference frame are system source, the spacecraft range in an inertial reference indicated by p E p S and pm respectively. Some extrasolar plan system may be computed. Absolute position can also be etary systems 5 are vieWable from the spacecraft. Each inde achieved through simultaneous observations of several pendent extrasolar planetary system 5 Would have a knoWn sources. Determining the range measurements of any unique unit vector in the inertial reference frame as Well as a knoWn set of three extrasolar planetary systems yields the location of stellar signature. a spacecraft in three dimensional space. [0032] Wavelength phase measurements can be thought of [0037] FIG. 4 depicts a spacecraft functional block diagram of one embodiment of the invention. A spectrum Wavelength as a total Wavelength phase that is the sum of some integer number of cycles plus a fraction of one cycle. These measure keps from one or more extrasolarplanetary system sources 6 is ments and their time of arrival can be merged and used by vieWable from the spacecraft 3. The spacecraft has an navigation softWare to determine position by employing a onboard computer 7 With hardWare components such as, but process similar to GPS integer cycle ambiguity resolution. not limited to, processor(s), memory, storage, busses, poWer The basic equation for GPS carrier phase pseudorange is Well sources, oscillators and/or timing sources. The onboard com knoWn in the literature and can be Written as Equation 5: puter 7 also has softWare processing capabilities and algo rithms that perform various navigation functions such as, but not limited to, signal processing, clock adjustments, ephem US 2013/0006449 A1 Jan. 3, 2013

eris and model propagation and ?ltering corrections (such as various components such as, but not limited to, processor(s), least squares or Kalman) to improve position and velocity memory, storage, busses, poWer sources, oscillators as Well as estimates. softWare algorithms and programs. The pure stellar spectrum [0038] The spacecraft 3 also has other subsystems 8. Sub template is eventually compared to the combined 12 gas cell systems 8 may include, but are not limited to, navigation units and stellar spectrum to derive the necessary radial velocities such as lMUs, star trackers, GPS receivers, horizon and sun [0043] With the present invention, data could also be col sensors. Subsystems 8 may also include, but are not limited lected from a potential astrometric interferometer. Mo st exist to, scienti?c instruments, guidance units, thrusters, propul ing star trackers are set up to detect some minimum light ?ux sion engines and communication systems. A data bus system intensity and then record the location of the light in the star 9 connects the onboard computer 7 to the spacecraft sub tracker’ s ?eld of vieW. lnterferometers obtain data in another systems 8 as Well as to one or more extrasolar planetary manner. The present invention apparatus may have various system star trackers, depicted as 10, 11 and 12 in FIG. 4. If embodiments With an interferometer, either Within the extra more than one extrasolar planetary system star tracker is solar planetary system star tracker apparatus itself, several located on a spacecraft, the orientation of their axes and ?elds devices located on the spacecraft platform or devices located of vieW may be chosen to optimiZe a function such as, but not on multiple spacecraft. limited to, vieWing different sources or redundancy. An extra [0044] Referring to FIG. 7, light from the target star is solar planetary system star tracker or sensor may be com collected by tWo subapertures and routed via minors to a prised of various components such as, but not limited to, beam splitter (a partially re?ective mirror) Where the tWo photocells, CCDs, gas absorption cells, processor(s), beams are combined. This combined beam Will exhibit con memory, storage, busses, poWer sources and oscillators. structive and destructive interference; the interference Will be [0039] The present invention incorporates advancements to at a maximum if there are equal optical path lengths from the traditional star trackers that have been used in the aerospace source to the beam splitter via the tWo arms. If the source industry. These star trackers have been integrated into space direction is shifted relative to the interferometer baseline, an craft platforms and most applications to date have used them additional path delay results in one beam external to the for corrections to IMU or ring laser gyro derived spacecraft interferometer. This path delay must be compensated by an attitudes. Individual star trackers have also been used during equal amount of path delay in the other beam internal to the the approach phase of rendeZvous operations to update a interferometer to maintain the maximum interference. This spacecraft’s relative Nay State. FIG. 5 depicts a typical star relationship can be Written as Equation 8: tracker. Major components usually include a light shade 13, a bright object sensor 14, a shutter mechanism 15, a protective WindoW 16, an adapter plate 17, and a main assembly instru Where B is the baseline vector (essentially the vector connect ment section 18 With connectors 19. ing the tWo subapertures), S is the unit vector to the star, C is [0040] The present extrasolar planetary system star tracker a constant (instrument bias) and the delay X is the amount of invention could still be employed for traditional uses. HoW internal path length necessary to equaliZe the path delays. ever, the greatest bene?ts are derived from the innovative Thus, the delay X is a measure of the angle betWeen the approaches implemented in the instrument package, namely interferometer baseline and the star unit vector. orbit and location determination and navigation capabilities [0045] The present invention apparatuses, systems and through utiliZation of Doppler spectroscopy and/or astrom methods disclosed in this application are envisioned to have etry. Doppler spectroscopy is achieved by placing a gas multiple forms, steps and embodiments. These can include, absorption cell or other similar device in the star tracker ?eld but are not limited to, various modi?cations, separate and/or of vieW. Another embodiment Would alloW potential astro integrated components, chipsets, boards, sensors and com metric data to be obtained With a photon collector or a Mich puter architectures as Well as similar or analogous hardWare elson interferometer. A navigation solution is determined or and softWare. re?ned by the radial velocities produced by Doppler spectros 1. A spacecraft extrasolar planetary star tracker apparatus, copy of a reference star With exoplanets and/or astrometric comprising: angular displacements and parallax measurements. a sensor to detect a spectrum from a star system With at [0041] An embodiment of the present invention may use least one exoplanet; and single aperture and/or interferometric equipment for astro a gas absorption cell placed betWeen the sensor and the star metric measurements. Radial velocity detection for Doppler system With at least one exoplanet such that the sensor spectroscopy may use the Fabry-Perot and/ or gas absorption can detect the spectrum from the star system With at least cell techniques. The preferred embodiment of the present one exoplanet through the gas absorption cell. invention star tracker system Would make use of an 12 gas 2. The apparatus of claim 1, Wherein the detected spectrum absorption cell. The 12 gas absorption cell technique has been is used to calculate radial velocity via Doppler spectroscopy. successful in the Earth based detection of exoplanets. The 3. The apparatus of claim 1, Wherein the detected spectrum main components consist of a translucent glass cell, heaters, measurements are used to calculate spacecraft position. temperature sensors, insulation and necessary electronics. 4. The apparatus of claim 1, Wherein the detected spectrum [0042] FIG. 6 depicts a block diagram preferred embodi measurements are accumulated and used to calculate a ?l ment of an extrasolar planetary system star tracker With a gas tered estimate of spacecraft position. absorption cell apparatus. Iodine gas is enclosed in a central 5. The apparatus of claim 1, Wherein the star system With at tube 20 and the Whole cell housing 21 is placed in the path of least one exoplanet is used to calculate spacecraft attitude. the stellar spectrum 6 being observed. The spectrometer CCD 6. A spacecraft navigation system using extrasolar plan 22 records the photons detected in the designated Wave etary star motion comprising: lengths for both the stellar spectrum 6 and the 12 gas cell a sensor located on a spacecraft to detect a spectrum from spectrum 23. The electronic package 24 may be comprised of a star system With at least one exoplanet; US 2013/0006449 A1 Jan. 3, 2013

a gas absorption cell located on the spacecraft placed selecting a reference star system With at least one exoplanet between the sensor and the star system With at least one from an onboard softWare database; exoplanet such that the sensor can detect the spectrum detecting a spectrum from the reference star system With at from the star system With at least one exoplanet through least one exoplanet through a gas absorption cell the gas absorption cell; onboard the spacecraft; a computer located on the spacecraft that is connected to using the detected spectrum from the reference star system the sensor by a data bus; With at least one exoplanet to calculate radial velocity a softWare algorithm located in the computer that can cal via Doppler spectroscopy; and culate radial velocities from the detected spectrum via incorporating the radial velocity calculations and the initial Doppler spectroscopy techniques; and estimate of spacecraft position into a ?ltered estimate of a softWare algorithm located in the computer that can cal spacecraft position. culate spacecraft position using the calculated radial 14. The method of claim 13, Wherein the means for ?ltering velocities from the detected spectrum. include a Kalman ?lter. 7. The system of claim 6, Wherein the computer has an 15. The method of claim 13, Wherein the ?ltered estimate additional softWare algorithm that is used in the process of of spacecraft position includes additional navigation sensor controlling the velocity of the spacecraft. measurements. 8. The system of claim 6, Wherein the calculated radial 16. The method of claim 13, Wherein the ?ltered estimate velocities are accumulated and used to calculate a ?ltered of spacecraft position includes Global Positioning System estimate of spacecraft position. measurements. 9. The system of claim 6, Wherein the softWare algorithm 17. The method of claim 13, Wherein the ?ltered estimate that calculates spacecraft position uses a Kalman ?lter. of spacecraft position includes Deep Space Network mea 10. The system of claim 6, Wherein the softWare algorithm surements. that calculates spacecraft position includes additional navi 18. The method of claim 13, Wherein onboard spacecraft gation sensor measurements. 11. The system of claim 6, Wherein the star system With at navigation is used in the process of controlling the velocity of least one exoplanet is used to calculate spacecraft attitude. the spacecraft. 12. The system of claim 6, Wherein there is more than one 19. The method of claim 13, Wherein the reference star sensor for the purposes of detecting different star system system With at least one exoplanet is also used to calculate spectrum simultaneously. spacecraft attitude. 13. A method for onboard spacecraft navigation using 20. The method of claim 13, Wherein onboard spacecraft extrasolar planetary star systems, the method comprising the navigation is used in the process of controlling the attitude of steps of: the spacecraft. having an initial estimate of a spacecraft position in an inertial reference frame;