Abstract:
A cubesat design includes selected subsystems for managing communications to other satellites and ground stations. In one embodiment, the subsystem includes a deployable antenna having compact size and low weight that reliably releases and detects an extended antenna after launch.

Description:
CROSS REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This disclosure incorporates by reference the following pending U.S. patent applications: (1) Ser. No. 13/757,062, title: System And Method For Widespread Low Cost Orbital Satellite Access filed on Feb. 1, 2014; (2) Ser. No. 13/961,875, title: Computerized Nano-Satellite Platform For Large Ocean Vessel Tracking filed on Aug. 7, 2014; and (3) Ser. No. 13/961,384, title: System And Method For High-Resolution Radio Occultation Measurement Through The Atmosphere filed on Aug. 7, 2013. Further, this disclosure incorporates by reference U.S. patent application Ser. No. ______ filed Oct. 15, 2014, titled Back-Plane Connector for Cubesat. The contents of these applications are incorporated by reference herein as if each was restated in full. 
     
    
     FIELD OF INVENTION 
       [0002]    The inventions herein are directed to novel systems and methods for supporting satellite design, manufacturing and operation. In particular, the present invention is directed to the design of small form factor satellites (known in the art as “cubesats”), including selected subsystems in satellite design directed to antenna storage and deployment. 
       BACKGROUND 
       [0003]    A growing interest in low earth orbit satellites having a small form factor has led to an increase in both launches of the vehicles and the recognition that earlier techniques for manufacturing and control thereof are inadequate because of the specialized size and weight criteria of a typical cubesat. While standardized to some extent, significant variations in design have taken hold in this industry. 
         [0004]    Due to their smaller size, cubesats generally cost less to build and deploy into orbit above the Earth. As a result, cubesats present opportunities for educational institutions, governments, and commercial entities to launch and deploy cubesats for a variety of purposes with fewer costs compared to traditional, large satellites. 
       SUMMARY 
       [0005]    One aspect of the present invention is directed to the satellite antenna design. Satellite communication with ground stations and other satellites is maintained in operation using deployable and deployed antenna. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements. 
           [0007]      FIG. 1  is an isometric diagram of the cubesat with a deployed antennae array; 
           [0008]      FIG. 2  is a plan cross-section diagram of the cubesat of  FIG. 1  depicting two coiled antenna prior to deployment; 
           [0009]      FIGS. 3 and 3A  illustrate a module antenna casing for storing and releasing a coiled antenna and a magnified view thereof; and 
           [0010]      FIGS. 4 and 4A  illustrate a second view of the modular design utilizing a release mechanism and a magnified view thereof. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent to those skilled in the art that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings. 
         [0012]    Certain challenges are presented when designing cubesats such as incorporating the desired structure and electronics into a relatively small form factor, maximizing the efficiency of the included components given volume and weight constraints, and providing sufficient communication systems to relay information to and from networked satellites within the constellation and ground-based systems. Imaging cubesats, for example, utilize much of the volume of the satellite for the imaging system, reducing the available space for other components, such as antennae for communication. Imaging cubesats can produce relatively large amounts of information making it desirable to incorporate a communication system capable of a relatively high data transmission rate, consequently making larger antenna systems more desirable. 
         [0013]    Cubesats can be advantageous where satellite capabilities are desirable but the cost to manufacture and launch a traditional, large satellite is prohibitively expensive. Cubesats are smaller and weigh less than traditional, large satellites and therefore are generally less costly to manufacture and launch into orbit. Challenges arise, however, in reducing the size of components and systems to fit into a cubesat while maintaining functionality. For instance, large satellites may include large communications antennae making high data transmission rates possible. Cubesats, on the other hand, are limited in the size of antenna that may be included, possibly reducing the data transmission rate available. The gain of the antenna may also be affected by the size of the antenna, affecting the link margin and size of corresponding communication systems. The gain of the antenna may also be affected by the frequency band of communication with the ground or other satellites. 
         [0014]    It would be advantageous, then, for a cubesat system to increase the gain of the antenna system, and the data transmission rate, while maintaining the size within a desired envelope and the communication frequency within an allocated band. 
         [0015]    To increase the utility of cubesats, therefore, it would be advantageous to incorporate a relatively high gain antenna into a small form factor of the cubesats. 
         [0016]    The present example provides a small form factor and light antenna with high gain capabilities. The cubesat, in one embodiment, is based on an industry standard, developed in 2001 by Stanford University and California Polytechnic Institute and described in the document “CubeSat Design Specification.” The size and sophistication of the satellite is such that it fits the overall design and objectives of the operative platform used to support it. The size of the satellite can be relatively small, in general not exceeding 10 cm×10 cm×30 cm and 10 kg of mass, and the design includes around 25 separate sensors connected to and in communication with the central processing unit of the satellite. These sensors include a plurality of frequency specific monitors such as UV (Ultraviolet) and IR (infrared); other sensors are for remote detection of surface temperature; spectroscopy and one or more accelerometers; other onboard devices include camera/vision systems for still and video capture. 
         [0017]      FIGS. 1 and 2  illustrate an example of a cubesat  10  which includes solar panels  20  to provide energy to the internal components of the cubesat  10 . In this example, there are two antenna housings  100  each enclosing a separate antenna  102 .  FIG. 1  illustrates both of the antennae  102  fully deployed.  FIG. 2  illustrates the undeployed antennae  102  and their individual deployment axes  104 . The deployment axes  104  are the axes over which the antennae  102  extend when deployed. In the present example, when the two housings  100  are mounted in the cubesat  10 , their deployment axes  104  form an angle a at 90° between them. 
         [0018]    Turning now to  FIGS. 2, 3, and 4 , a series of figures illustrate different views of antenna storage and deployment subsystem. As depicted in  FIG. 2 , the antenna  104  is coiled into a shaped containment slot  106 . The containment slot  106  includes an antenna anchor point  108  and a recess  110  to hold the coiled antenna  102 . The housing  100  also includes a door  112  that can allow selectable access to the recess  110 . The door  112  is connected to hinge  114  and the housing  100  on door side proximal to hinge  114 , and detachably anchored on the distal end. The door  112  is detachably engaged in its closed position by holding pin  116 . 
         [0019]    The antenna  102  itself is formed of a thin aluminum metal sheet with a selected spring constant. While the metal is thin, it can be cambered (curved) along its shorter axis to increase rigidity. This concept is also used for metal tape measures. The metal is thin enough to coil, but once uncoiled, the camber provides enough stiffness that the antenna  102  is linearly deployed and does not fold, flop or droop. 
         [0020]    During storage and launch, the coiled antenna  102  is held compressed and in place in the containment slot  106  by door  112 , that defines an antenna containment space. When the door  112  is shut, the antenna  102  exerts some spring pressure against the door  112 , but the antenna  102  is held fast by door  112 . The coiled shape of the antenna  102  conforms to the recess  110 , which is sized for the coiled antenna  102  and prevents the antenna  102  to expand in any direction except the opening created by door  112 . 
         [0021]    In one embodiment, there is a single door  112  on one wall that is opened by a signal controlled latching mechanism  200 , releasing the antenna  102 , thus allowing the unfurling extension of the metal antenna  102  to its final linear shape driven by the spring force of the metal.  FIG. 2  illustrates the open door  112  and the coiled antenna  102 . As depicted, the opening created by Door  112  allows for the unfurling of an exemplary 24 inch antenna through this passageway. 
         [0022]    Turning now to the signal controlled latching mechanism  200 , as illustrated in  FIGS. 3A and 4A . The coiled antenna  102  resides in its containment slot  106  in the housing  100  on the satellite  10  pressed against the latched door  112 . In one example of the signal controlled latching mechanism  200 , a thin wire  202  wraps around the holding pin  116  and is secured to the housing  100 . In this example, the wire  202  is secured through apertures  204  in the housing  100 . In one specific example, the thin wire  202  is made from monofilament UHDPE (ultra-high-density polyethylene) that is 10 mm thick. The wire  202  has sufficient strength to hold the door  112  closed against the spring force of the coiled antenna  102 . The wire  202  is “tied” through the apertures  204  and positioned so that the wire is juxtaposed against two resistors,  206 . Once in place, the wire is wrapped around the pin  116 , the door  112  is held closed. The antenna  102  is deployed by a signal that applies a current across the resistors  206  causing the plastic wire  202  to melt and break. 
         [0023]      FIGS. 1 and 2  illustrate the door  112  in the fully open or deployed position. In one example, the door  112  can be held in the open position or allowed to freely pivot after the antenna is deployed. 
         [0024]    The example of the latching mechanism  200  and antenna  102  minimizes both weight and components required for operation. The door  112  pivots at hinge  114  and, because movement is driven by the coiled spring force of the antenna  102 , the door does not require a separate spring loaded hinge to open, saving weight. Further, the use of the wire  202 , also simplifies the locking of the door  112 . 
         [0025]    Another feature of the present system is a deployment confirmation system  300  (or an AIS “automatic identification system”). When the proper signal is provided to the latch mechanism  200 , the resistors  206  are energized, melting the wire  202  and as the door swings open, the spring force in coiled antenna  102  causes the unraveling of coil to force the door  112  open to a full open position. When the door  112  is its full open position, a contact arm  118  bridges two contacts  302  which creates a connection (e.g. closes a circuit) triggering a signal to the system  300  confirming that door  112  has reached its full open position—allowing the antenna deployment. The contacts  302  are provided by two screws that close the circuit, creating the “antenna deployed” signal. 
         [0026]    While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.