RELATED FIELD OF TECHNOLOGY

The presently disclosed subject matter relates to the field of miniature satellites. BACKGROUND Miniature satellites are artificial satellites of low mass and size, usually under 500 kg.

Reducing satellite size and mass can provide various advantages, including reduced costs, which are achieved due to less costly design and manufacturing, and the use of smaller launching rockets.

Nanosatell ^' rtes is a term applied to a sub-category of miniature satellites and is commonly applied to satellites with a mass lower than 70 kg. Nanosatellites may be launched and operated together in a group of multiple satellites, providing sometimes equal or even better performance at a lower cost, as compared to that of single larger satellite.

GENERAL DESCRIPTION

Signal intelligence (SIGINT) is a form of intelligence gathering by intercepting signals. SIGINT collection systems are configured to detect and analyze communication signals which are being transmitted, and to identify and intercept specific signals of interest. Signal interception enables to gather information with respect to the transmitted data (e.g. COMINT collection and analysis). Furthermore, SIGINT collection systems, which comprise multiple receiving platforms (e.g. satellites) located at different points, can be used for determining the position of the transmitting units (i.e. units from which the intercepted signals are emanating). Determination of the position of a transmitting unit can be accomplished using various techniques such as triangulation, time of arrival methods, Doppler localization, etc. The intercepted signal can be further analyzed to obtain additional information such as the deployment formation of the transmitting units in a certain area of interest (i.e. area being monitored by a SIGINT collection system), the range of mobility of the transmitting units, specific role of different transmitting units, as well as the interrelations between the different transmitting units. According to some examples of the presently disclosed subject matter, nanosatellites operating in a group (referred to herein as a "nanosatellite formation" of "nanosatellites flight- formation") are configured to operate as a SIGINT collection system. Once a satellite formation is launched to a desired location in space, it can be operated for targeting various transmitting units. As mentioned above, using nanosatellites helps to reduce costs related to manufacturing and launching of the satellites in a formation.

Communication intelligence (COM I NT) is a sub-category of SIGINT that pertains to messages or voice information derived from interception of communication signals. Electronic intelligence (ELI NT) is another sub-category of SIGINT that includes non-communication electromagnetic radiation emanating from various emitters. For example, geo-location of ships and aircrafts can be determined based on the interception and analysis of their radar and other electromagnetic radiation emanating therefrom.

Communication signals related to different SIGINT types are identifiable by various characteristics, including for example, specific modulation, transmission bandwidth and frequency. In addition to the difference between SIGINT types, communication signals used by different transmitting units, as well as the electromagnetic radiation emanating from such units (or a respective body carrying the transmitting units), are characterized by different frequency ranges. In order to enable the interception of different types of transmission signals, an intercepting platform (e.g. satellite or other aircraft) is equipped with different types of antennas, each designed for receiving signals in a certain frequency band.

Nanosatellites are not sufficiently large for carrying a large satellite dish needed for intercepting high frequency signals which are transmitted over large distances (the greater the frequency of the signal, the greater the decay of the signal intensity over distance).

According to some examples of the presently disclosed subject matter, there is provided a nanosatellite, comprising: one or more panels configured for providing mechanical support to the nanosatellite, wherein at least one of the panels is designed as a parabolic antenna constructed from a conductive material having a concave shape and characterized by a certain gain, the antenna being capable of receiving signal transmission in a first frequency band.

The nanosatellite according to the above aspect of the presently disclosed subject matter can optionally comprise one or more of the features (i-xii) below in any technically possible combination or permutation: i. Wherein the antenna is a hybrid antenna comprising a groove within the thickness of the concave shape of the antenna; the groove is designed to operate as a second antenna for receiving signals transmitted in a second predefined frequency band; wherein the second frequency band at least partially does not overlap the first frequency band. ii. Wherein the antenna is a hybrid antenna comprising a groove within the thickness of the concave shape of the antenna; the groove comprises a second antenna made of a conductive material configured to receive signals transmitted in a second frequency band; wherein the second frequency band at least partially does not overlap the first frequency range. iii. Wherein the groove is characterized by a spiral shape. iv. Wherein the antenna is a hybrid antenna comprising a second antenna fixed on top the thickness of the concave shape of the antenna; the second antenna is designed to operate for receiving signals transmitted in a second predefined frequency band; wherein the second frequency band at least partially does not overlap the first frequency band. v. Wherein the first frequency band comprises high frequency signals in the range of 1 GHz to 10 GHz and the second frequency band comprises low frequency bands in the range of

100 MHz to 1 GHz. vi. Wherein the nanosatellite is launched as part of a flight-formation of nanosatellites comprising at least two satellites, each nanosatellite comprises a control unit configured to modify drag force exerted on the satellite for the purpose of changing the satellite's velocity and maintaining a desired distance from other satellites in the flight-formation.

vii. Wherein the control unit is further configured to modify drag force exerted on the satellite for changing velocity for the purpose of changing the satellite's orbit. viii. Wherein the control unit is configured for modifying the drag force exerted on the satellite to: determine self-positioning data; obtain additional positioning data pertaining to the position of at least one other nanosatellite in the formation; determine, based on the self- positioning data, the additional positioning data and data with respect to a planned orbit, whether the nanosatellite is drifting out of orbit; and if it is, generate maneuvering instructions for changing the orientation of the nanosatellite in order to control the velocity of the nanosatellite .

ix. Wherein the flight-formation comprises at least three nanosatellites.

x. Wherein the flight-formation is deployed for collecting SIGINT.

xi. Wherein the hybrid antenna is configured for collecting COM I NT and/or ELI NT. xii. Wherein the nanosatellite is structurally designed to be compactly packed together in a nanosatellite package comprising a plurality of nanosatellites.

According to another aspect of the presently disclosed subject matter there is provided a nanosatellite capable of operating in satellite flight-formation, the formation comprising at least two nanosatellites, wherein the nanosatellite comprises: a control unit configured to modify drag force exerted on the nanosatellite for changing the satellite's velocity in order to maintain a desired distance from other nanosatellites in the flight-formation and avoid breaking flight-formation; wherein, according to some examples, the control unit is configured for modifying the drag force exerted on the satellite, to: determine self-positioning data; obtain additional positioning data pertaining to the position of at least one other nanosatellite in the formation; determine, based on the self- positioning data and the additional positioning data and data with respect to a planned orbit, whether the nanosatellite is drifting out flight-formation; and if it is, generate maneuvering instructions for changing the orientation of the nanosatellite in order to control drag of the nanosatellite. According to some examples, the nanosatellite comprises actuators, wherein the maneuvering instructions are used for controlling the actuators for changing the attitude of the nanosatellite with respect to the heading of the satellite.

According to another aspect of the presently disclosed subject matter there is provided a subsystem configured to operate in a nanosatellite operable in a flight-formation, the flight- formation comprising at least two nanosatellites, the attitude control unit being configured to modify drag force exerted on the satellite for the purpose of changing the satellite's velocity and maintaining a desired distance from other satellites in the flight-formation to maintain the flight- formation. According to another aspect of the presently disclosed subject matter there is provided in a nanosatellite operating in a satellite flight-formation, the flight-formation comprising at least two nanosatellites, a method of controlling the orientation of the nanosatellite, comprising: controlling the nanosatellite orientation for the purpose of modifying drag force exerted on the satellite, thereby changing the satellite's velocity and maintaining a desired distance from other satellites in the formation.

According to some examples the method further comprises: determining self-positioning data; obtaining additional positioning data pertaining to the position of at least one other nanosatellite in the formation; determining, based on the self- positioning data and the additional positioning data, and data with respect to a planned orbit, whether the nanosatellite is drifting out of flight-formation; and if it is, generating maneuvering instructions for changing the orientation of the nanosatellite in order to control nanosatellite drag of the nanosatellite for controlling its velocity and maintaining flight-formation.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. la shows a schematic illustration of a satellite with a satellite body integrated antenna, according to some examples of the presently disclosed subject matter;

Fig. lb shows a schematic illustration of a hybrid antenna, according to some examples of the presently disclosed subject matter; Fig.2 shows a schematic illustration of a nanosatellite flight-formation, according to some examples of the presently disclosed subject matter;

Fig. 3a shows a schematic illustration of three nanosatellites packed and unpacked respectively, according to some examples of the presently disclosed subject matter;

Fig.3b is a schematic illustration showing three nanosatellites stacked one over the other, according to some examples of the presently disclosed subject matter;

Fig. 4 is a functional block diagram of a nanosatellite system according to some examples of the presently disclosed subject matter;

Fig. 5 is a flowchart illustrating a sequence of operations performed according to some examples of the presently disclosed subject matter; and Fig. 6 is a schematic illustration showing the dimensions of a satellite integrated antenna, according to some examples of the presently disclosed subject matter.

It is noted that the drawing are not drawn to scale.

DETAILED DESCRIPTION

As used herein, the phrase "for example," "such as" and variants thereof describing exemplary implementations of the present invention, are exemplary in nature and not limiting.

As used herein the terms "one or more" and "at least one" aim to include one as well any number greater than one e.g. two, three, four, etc.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub- combination. While the invention has been shown and described with respect to particular embodiments, it is not thus limited.

In embodiments of the invention, fewer, more and/or different stages than those shown in Fig.5 may be executed. In embodiments of the invention, one or more stages illustrated in Fig. 5 may be executed in a different order and/or one or more groups of stages may be executed simultaneously. Fig. 4 illustrates a schematic of the system architecture in accordance with embodiments of the invention. Elements in Fig.4 can be made up of any combination of software and hardware and/or firmware that performs the functions as defined and explained herein. According to other examples of the presently disclosed subject matter, the system may comprise fewer, more and/or different elements than those shown in Fig. 4.

Bearing the above in mind, attention is now drawn to Fig. la showing a schematic illustration of a satellite with a satellite body integrated antenna, according to some examples of the presently disclosed subject matter. In general, satellites comprise several subsystems, each designated for performing different tasks. These subsystems include, inter alia, a structural subsystem, a telemetry subsystem, a power subsystem, a thermal control subsystem and an orientation and orbit control subsystem (comprising for example an attitude control unit). Satellite 100 can comprise these subsystems as well as additional subsystems such as an imaging subsystem (including for example one or more cameras and/or other imaging devices) and a communication payload configured to enable data transmission to and from the satellite. Notably, not all subsystems are shown in Fig. la.

The structural subsystem provides the mechanical infrastructure (satellite housing) for holding together all the satellite subsystems and components and providing the required durability to withstand mechanical stress and extreme temperatures during launch and while in orbit. The telemetry subsystem is configured to monitor, adjust and control the onboard equipment operation and transmits equipment operation data to the earth control system.

The power subsystem can comprise for example solar panels configured to absorb and convert solar energy into electrical power as well as batteries configured to store electric power and supply power to the satellite subsystems during periods of time when the sun is shadowed by the earth and solar energy is unavailable.

The thermal control subsystem is configured to regulate the internal temperature of the satellite subsystems and protect the onboard equipment from the extreme temperatures to which the satellite is exposed.

The orientation and orbit control subsystem is configured in general to maintain the satellite in a desired orbital position and maintain the antennas directed to the desired area of interest (e.g. an area from which it is desired to collect SIGINT). In case of a satellite operating in a flight-formation orientation and orbit control subsystem (e.g. with the help of attitude control unit), it is further configured to maintain the satellites in a desired formation during orbit.

The orientation and orbit control subsystem further comprises various actuators, such as reaction wheels and thrusters which are controlled by the flight controller and enable to adjust and control the orientation and orbit position of the satellite.

According to the presently disclosed subject matter, a satellite with a body integrated antenna is disclosed. As illustrated in Fig. la, in satellite 100 antenna 103 is integrated as part of the structural subsystem. The satellite body is characterized by a new structural design where antenna 103 is integrated as part of one of satellite's side panels. As illustrated in Fig. la nanosatellite 100 comprises an opening at one of its side panels where a parabolic antenna (satellite dish) is fitted. The side panel can be designed as two parts which are put together (i.e. the concave area

9 and flat area 10 being separate parts assembled together). According to an optional design, rather than an antenna being fitted in an opening, the side panel may be constructed from one or more sheets of bent material (e.g. metal or carbon fiber or a combination thereof) comprising the entire side panel, including both the concave area 9 and the flat area 10. According to some examples the entire satellite can be constructed from a single bent martial (e.g. metal or carbon fiber) shaped in a desired shape including concave area 9 providing the antenna.

It is noted that although Fig. la shows antenna 103 covering only part of the respective side panel (the rest of the side panel comprising flat surface 10), this is not necessarily so, and in some alternative designs the entire side panel can comprise the antenna 103, e.g. the concave part can emerge directly from the side panels.

Once fitted in its place, antenna 103 serves, in addition to its traditional function of receiving signals, as a side panel (or wall) structurally supporting satellite 100. Other components of the satellite related to the various satellite subsystems are arranged within the internal space of the satellite structure located between the satellite side panels (indicated in Fig. 1 as panels A to E) and the internal part of antenna 103. The specific arrangement of the various components within the satellite's inner space is determined based on the specific shape, which can be also influenced by the convex shape of the internal part of antenna 103 as well as based on other considerations as known in the art (e.g. center of gravity). Notably, while in Fig. la the satellite is drawn with a substantially rectangular shape, this may not necessarily be so, and in other examples satellite 100 may be designed differently (e.g. having a rounder contour).

Fig. 6 is a schematic illustration showing the dimensions of a satellite integrated antenna, in accordance with examples of the presently disclosed subject matter. As mentioned above, certain tasks (e.g. related to SIGINT collection) require using satellite formations comprising multiple satellites. The satellites in a flight-formation orbit the earth, each satellite in the flight-formation assuming a certain position with respect to the other satellites in the formation. The flight-formation of the satellites can be predefined by flight-formation data, determining the relative position of each satellite with respect to other satellites in the formation.

Satellites in a flight-formation may drift out of formation, due to, for example, atmospheric drag, which is more problematic in lower orbiting altitudes. Commonly, drifting of satellites out of formation (or more generally out of orbit) necessitates reboost maneuvers in order to redirect the satellite back to its desired location. Reboost maneuvers are carried out with the help of thrusters, which consume the limited fuel stored onboard the satellite, and thus contribute to shortening the satellites' lifetime. Thrusters, as well as fuel needed for operating the thrusters which are loaded on a satellite, increase the weight of the satellite. Therefore it is advantageous to reduce the size of the thrusters and the amount of fuel which is loaded onboard the satellite. This demand is especially important in nanosatellites, which are naturally characterized by even greater limitations on their weight and the equipment they can carry.

According to some examples of the presently disclosed subject matter, a nanosatellite is configured to maintain a desired orbit and a desired position with respect to other nanosatellites in a formation, by changing the orientation of the satellite. Due to differences in size and possibly also in the shape of different faces of the nanosatellite, changing the orientation of a nanosatellite with respect to its heading has an effect on the drag acting on the satellite. The change in drag can result in an increase (and in some cases, a decrease) in the nanosatellite's velocity. Controlling the velocity of a nanosatellite relative to the velocity of other nanosatellites in the same flight-formation enables to avoid drifting of the nanosatellite out of formation.

Controlling nanosatellite drag for the purpose of controlling nanosatellite velocity and maintaining the nanosatellite within a desired nanosatellite formation as disclosed herein can be performed by nanosatellites having a body integrated antenna as disclosed hereinabove (and possibly also a substantially rectangular shape). Controlling nanosatellite drag for the purpose of controlling nanosatellite velocity and maintaining the nanosatellite within a desired satellite formation, as disclosed herein can be also performed by nanosatellites having a folded antenna. Such a folded antenna can be used instead of the body integrated antenna. Folded antennas are generally known in the art and are designed as a foldable element capable of being folded while the nanosatellites are stacked, and which automatically unfold following launch of a nanosatellite stack.

Fig. 2 is a schematic illustration showing a nanosatellite with a body integrated antenna as disclosed herein, in different orientations. The arrows extending from each satellite in the figure demonstrate a respective progression vector. Notably, Fig. 2 shows variations in the pitch component of the orientation. Different or additional components of the orientations (including pitch, yaw and roll) can be likewise modified in order to maintain a desired satellite orbit and a desired formation.

Furthermore, the shape (e.g. rectangular shape) and compact packaging of satellite 100 enables to compactly pack multiple nanosatellites together. Packing a plurality of satellites together is advantageous during the launching of a satellite formation. Also, this may be advantageous during transport of satellites from one place to another.

Fig. 3a shows a schematic illustration of three nanosatellites unpacked 30 and packed 31, according to examples of the presently disclosed subject matter. As exemplified in Fig 3a nanosatellites are designed to enable the compact packing of multiple satellites in a condensed package (or stack).

Fig.3b is a schematic illustration showing three nanosatellites stacked one over the other, according to an example of the presently disclosed subject matter.

Fig. 4 is a functional block diagram of a satellite system, according to some examples of the presently disclosed subject matter. Satellite system 400 comprises a plurality of subsystems, orientation and orbit control subsystem 402, communication subsystem 403, SIGINT collection subsystem 405 and various additional subsystems 407 such as a power subsystem and thermal control subsystem which were mentioned above. Orientation and orbit control subsystem can comprise attitude control unit 401. Attitude control unit 401 can comprise for example sensors 411, formation data input module 413, orbit and formation unit 415 and actuators control unit 417.

According to an example of the presently disclosed subject matter, each nanosatellite in a satellite formation, comprises an attitude control unit configured to determine or otherwise obtain the satellite position in space and the (relative) position of the at least one other satellite in the same flight-formation. The attitude control unit onboard each satellite is configured to maintain the flight-formation by keeping the satellite in a desired orbit and keeping a desired position relative to at least one other satellite in the formation. Thus, attitude control unit can be configured to use information pertaining to the respective location relative to other nanosatellites in the formation, obtained from one or more other satellites (e.g. by communication subsystem 403).

Fig. 5 is a flowchart of operations carried out by a nanosatellite, according to an example of the presently disclosed subject matter. Operations described below with reference to Fig. 5 are described by way of example with reference to functional elements in satellite system 400 described above with reference to Fig. 4, however this should not be construed as limiting. Functional elements in satellite system 400 include at least one computerized device (e.g. main control unit 420 and attitude control unit 401) with data processing capabilities which can comprise or be operatively connected to one or more processing circuitries, which include a processing device such as a processor (e.g. digital signal processor (DSP), microcontroller, field programmable circuit (ASIC), etc.) or be otherwise connected to a device (e.g. computer device of some sort) comprising one or more processors.

The nanosatellites can be launched as a satellite stack comprising a plurality of nanosatellites. After launch of a nanosatellites stack, the satellites proceed to orbit the earth in a predefined (or controlled) flight-formation. The flight-formation defines relative distances and positions of the plurality of nanosatellites, one with respect to the other. Once in orbit, the nanosatellites in the flight-formation are configured to maintain their position in orbit and maintain their relative position to avoid breaking the flight-formation.

To this end, each nanosatellite is configured to determine self-positioning data including for example, position, orientation, velocity and heading of the satellite (block 501). Positioning data can be determined with the help of sensors 411 which can include for example a GPS unit and star tracker unit. Nanosatellites in a formation can communicate with each other (e.g. with the help of communication subsystem 403) in order to allow each nanosatellite to obtain positioning data of at least one other satellite in the formation (block 503). Based on self-positioning data as well as information indicating a planned orbit, a nanosatellite can be configured to determine (e.g. with the help of control unit 420) whether the nanosatellite is drifting out of orbit. Furthermore, based on the self-positioning data and positioning data of at least one other satellite in the formation and information indicating a predefined flight-formation (including for example desired distance between nanosatellites), each satellite can be configured to determine whether the flight-formation is breaking or about to break (block 505). Information indicating the required flight-formation settings can be stored in formation data input module 413. In the event that the processing output indicates that the nanosatellite is drifting out of orbit or out of flight-formation, the nanosatellite is configured to generate maneuvering instructions for directing the satellite back into orbit and/or back into flight-formation (block 507). According to an example, orbit and formation unit 415 is configured to use self- positioning data and positioning data of at least one other nanosatellite in the formation in order to execute the operations described with respect to blocks 505 and 507.

The maneuvering instructions can be used for controlling respective devices for changing the nanosatellite orientation (including one or more of pitch, yaw and roll) of the satellite's body with respect to its heading, in order to redirect the satellite to drift at the desired altitude (block 509). According to the presently disclosed subject matter, a nanosatellite in the formation is maneuvered by changing the orientation of the satellite body with respect to the heading of the satellite. Depending on the satellite's orientation, the drag which is exerted on the satellite can be increased or decreased, and accordingly the velocity of the satellite can be controlled. Maneuvering the nanosatellites by changing their relative orientation enables to control the satellite formation without using a boost engine or fuel.

For example, orbit and formation unit 415 can be configured to determine a desired velocity of the nanosatellite, which would avoid drifting the nanosatellite away from one or more other nanosatellites in the flight-formation, maintaining the nanosatellites in the flight- formation, and feeding respective instructions to actuator control units 417 for controlling the satellite and changing its orientation, thereby controlling the drag exerted on the satellite and thus obtaining the desired velocity. This process can be repeated (e.g. in a continuous feedback loop) in order to constantly maintain the nanosatellites in a desired orbit and formation.

As mentioned above, reception of signals transmitted at high frequencies (e.g. in the range of 1 GHz to 10 GHz) require high gain parabolic antennas such as satellite dishes, while signals transmitted at lower frequencies (e.g. in the range of 100 MHz to 1 GHz including for example, VHF and UHF signals) require other antenna types such as coil or dipole antennas. According to the presently disclosed subject matter, a new type of antenna (referred to herein as a "hybrid antenna") is introduced, which is configured to receive signals transmitted in a larger frequency range, and which includes signals in both high frequency and low frequencies mentioned above.

Reverting to Fig. lb it shows a schematic illustration of a hybrid antenna in accordance with an example of the presently disclosed subject matter. A hybrid antenna can be integrated as part of the nanosatellite body, as explained above with reference to Fig. la. Antenna 103 (a high frequency antenna) is a parabolic antenna designed with a certain gain. A second antenna 105 is configured to receive signals transmitted at frequencies lower than those received by antenna 103. Antenna 105 (a low frequency antenna) is designed as an integral part of antenna 103. According to one example, as illustrated in Fig. lb, antenna 105 is configured as a spiral groove within the thickness of the conductive material of parabolic antenna 103. The groove within the conductive material is designed to operate as an antenna for receiving signals within a certain frequency range. According to other examples, the groove may be filled or replaced with an actual antenna conductor material (e.g. a material different than the material from which antenna 103 is made). According to other examples, antenna 105 can be attached on top of the parabolic antenna rather than be placed in a groove.

Hybrid antenna 101 disclosed herein is configured to receive a wider range of signals transmitted in a wider frequency band, where part of the signals are received by parabolic antenna 103 and part of the signals are received by antenna 105. Thus, a nanosatellite formation comprising multiple nanosatellites, each equipped with a hybrid antenna as disclosed herein, can monitor different types of SIGINT data.

For example both COMINT (normally comprising signals in the lower frequency range) and ELINT (normally comprising signals in the higher frequency range) can be received by hybrid antenna 101. The former SIGINT type can be received by antenna 105 and the latter type of SIGINT can be received by antenna 103. Furthermore, hybrid antenna 101 provides an elegant design which consumes less space on the satellite and has less effect on satellite drag.

It is to be understood that the presently disclosed subject matter is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The presently disclosed subject matter is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as basis for designing other structures, methods, and systems for carrying out the several purposes of the presently disclosed subject matter.