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  • 1. 1 ABSTRACT THE OUTERNET There are more computing devices in the world than people, yet less than 40% of the global population has access to the wealth of knowledge found on the Internet. The price of smart phones and tablets is dropping year after year, but the price of data in many parts of the world continues to be unaffordable for the majority of global citizens. In some places, such as rural areas and remote regions, cell towers and Internet cables simply don't exist. The primary objective of the Outernet is to bridge the global information divide. Access to knowledge and information is a human right and Outernet will guarantee this right by taking a practical approach to information delivery. By transmitting digital content to mobile devices, simple antennae, and existing satellite dishes, a basic level of news, information, education, and entertainment will be available to all of humanity. Although Outernet's near-term goal is to provide the entire world with broadcast data, the long-term vision includes the addition of two-way Internet access for everyone. For free. Outernet consists of a constellation of low-cost, miniature satellites known as ‗Cubesats‘ in Low Earth Orbit. Each satellite receives data streams from a network of ground stations and transmits that data in a continuous loop until new content is received. In order to serve the widest possible audience, the entire constellation utilizes globally-accepted, standards-based protocols, such as DVB(Digital Video Broadcasting), Digital Radio Mondiale, and UDP-based WiFi multicasting. RAJANISH KUMAWAT Enroll no.- 10E1SOECM3XT092
  • 2. 2 Chapter-1 INTRODUCTION 1.1 Outernet: The Outernet is a global networking project currently under development by the Media Development Investment Fund (MDIF), a United States-based non-profit organization established in 1995. The Outernet's goal is to provide free access to internet data through wifi, made available effectively to all parts of the world. The project would involve using datacasting and User Datagram Protocol through hundreds of CubeSats measuring 10 cm (3.9 in) each. Wi-fi enabled devices would communicate with the satellites in their region, which in-turn communicate with other satellites and ground-based networks, thus forming the global network. The network would initially support only one-way traffic, with two-way traffic being implemented once adequate funding is raised. Initial prototype satellite deployments is planned for June 2014, with the final deployment run scheduled for mid-2015. According to MDIF, the initial content access includes international and local news, crop prices for farmers, Teachers Without Borders, emergency communications such as disaster relief, applications and content such as Ubuntu, movies, music games, and Wikipedia in its entirety. MDIF plans to formally request NASA to use the International Space Station to test their technology in September 2014. Manufacturing and launching of satellites would begin in early 2015, and Outernet is planned to begin broadcasting in June 2015. India based "Spacify Inc." is a private non-profit company by Silicon Valley based technocrat and entrepreneur Siddharth Rajhans along with Space debris mitigation expert Sourabh Kaushal, which is privately working on using this technology to provide global free wi-fi access.
  • 3. 3 A small team of workers at a New York based non-profit organization called Media Development Investment Fund (MDIF) has announced its intention to build an "Outernet"—a global network of cube satellites broadcasting Internet data to virtually any person on the planet—for free. The idea, the MDIF website says, is to offer free Internet access to all people, regardless of location, bypassing filtering or other means of censorship. As the Internet has grown in size and importance, human rights organizations, or those (such as MDIF) promoting freedom of expression, have begun to propose that access to the information that the Internet can provide, is a basic human right. Conversely, they suggest that restricting access to the Internet is a violation of human rights. MDIF seeks to circumvent those that might wish to violate such human rights by bypassing their ability to restrict access—they are proposing that hundreds of cube satellites be built and launched to create a constellation of sorts in the sky, allowing anyone with a phone or computer to access Internet data sent to the satellites by several hundred ground stations. MDIF claims that 40 percent of the people in the world today are still not able to connect to the Internet—and it's not just because of restrictive governments such as North Korea—it's also due to the high cost of bringing service to remote areas. An Outernet would allow people from Siberia to parts of the western United States to remote islands or villages in Africa to receive the same news as those in New York, Tokyo, Moscow or Islamabad. That they say, would guarantee all people the same Internet rights as everyone else. The Outernet, as envisioned, would be one-way—data would flow from feeders to the satellites which would broadcast to all below. MDIF plans to add the ability to transmit from anywhere as well as soon as funds become available. At this time, it's not clear how much MDIF has been able to collect for the project, but acknowledge that building such a network would not be cheap. Such satellites typically run $100,000 to $300,000 to build and launch. Still, the timeline for the project calls for deploying the initial cubesats as early as next summer.
  • 4. 4 Figure1(a):- Outernet Plan or Idea 1.2 Need of Outernet: There are more computing devices in the world than people, yet less than 40% of the global population has access to the wealth of knowledge found on the Internet. The price of smartphones and tablets is dropping year after year, but the price of data in many parts of the world continues to be unaffordable for the majority of global citizens. In some places, such as rural areas and remote regions, cell towers and Internet cables simply don't exist. The primary objective of the Outernet is to bridge the global information divide. Broadcasting data allows citizens to reduce their reliance on costly Internet data plans in places where monthly fees are too expensive for average citizens. And offering continuously updated web content from space bypasses censorship of the Internet. An additional benefit of a unidirectional information network is the creation of a global notification system during emergencies and natural disasters. Access to knowledge and information is a human right and Outernet will guarantee this right by taking a practical approach to information delivery. By transmitting digital content to mobile
  • 5. 5 devices, simple antennae, and existing satellite dishes, a basic level of news, information, education, and entertainment will be available to all of humanity. Although Outernet's near-term goal is to provide the entire world with broadcast data, the long- term vision includes the addition of two-way Internet access for everyone. For free. Satellites need to be controlled from earth to fully utilize their functionality. To do this optimally satellites need the longest and most frequent possible communication access times with their groundstations. Large satellites currently use services such as NASA‘s Tracking and Data Relay(TDRS), and distributed ground station networks such as SSC‘s PrioraNet. These services are however very expensive and not available for commercial use. The launch of micro-, nano- and pico-satellites are rapidly increasing among smaller companies and universities. The use of above mentioned TT&C services are not economically feasible for these smaller satellite missions. The only option left for these projects is to build and maintain a small ground station which can amount up to a third of the total mission budget. 1.3 Mission Objectives: To address this shortfall the following mission objectives are set: - Provide a communication opportunity to any satellite in Low Earth Orbit (LEO) at least once each orbit. - Provide this service to worst-case communication link budget client, namely a 1U CubeSat with VHF/UHF monopole - The service should be cheaper to use than constructing and maintaining a small ground station over the mission lifetime
  • 6. 6 Chapter-2 HOW IT WORKS 2.1 How Does It Work: Outernet consists of a constellation of low-cost, miniature satellites in Low Earth Orbit. Each satellite receives data streams from a network of ground stations and transmits that data in a continuous loop until new content is received. In order to serve the widest possible audience, the entire constellation utilizes globally-accepted, standards-based protocols, such as DVB, Digital Radio Mondiale, and UDP-based WiFi multicasting. Citizens from all over the world, through SMS and feature-phone apps, participate in building the information priority list. Users of Outernet's website also make suggestions for content to broadcast; lack of an Internet connection should not prevent anyone from learning about current events, trending topics, and innovative ideas. 2.2 The project consists of three segments: 1. The Space Segment 2. The Ground Segment and 3. The User Segment. The space segment (OuterNet) consists of 14 satellites evenly spaced in a 900km circular equatorial orbit. The constellation‘s beam width coverage is such that all LEO satellites in orbits below 600km altitude will come into range of the constellation at least once every orbit (refer to orbit/constellation design for details). When within range, the client satellites can be polled by the constellation to download telemetry and/or upload tele-commands.
  • 7. 7 Figure 2(a): Conceptual Illustration of the OuterNet The ground segment consists of several ground stations spread around the equator. Due to the constellation‘s equatorial orbit, each of the satellites will pass every ground station during every orbit. Three potential ground stations have already been identified: Guiana Space Centre, Broglio Space Centre and Pusat Remote Sensing. The user segment consists of clients who register to use the OuterNet service. Pricing will be based on the amount and frequency of data relayed. Satellite operators will be able to configure their TT&C schedules, download telemetry, upload telecommands and configure their communications protocol and modulation technique through a user friendly internet interface.
  • 8. 8 Figure 2(b): Interfacing between system segments Broadcasting data allows citizens to reduce their reliance on costly Internet data plans in places where monthly fees are too expensive for average citizens. And offering continuously updated web content from space bypasses censorship of the Internet. An additional benefit of a unidirectional information network is the creation of a global notification system during emergencies and natural disasters. Access to knowledge and information is a human right and Outernet will guarantee this right by taking a practical approach to information delivery. By transmitting digital content to mobile devices, simple antennae, and existing satellite dishes, a basic level of news, information, education, and entertainment will be available to all of humanity. 2.3 Key Performance Parameters: The key performance parameters for the proposed mission are: (a) Communication latency (b) Communication Power (c) Data Capacity (d) Target Orbit
  • 9. 9 2.3.1 Communication latency: The time it takes for the client satellite to move into range of the constellation communication footprint. It is dependent on the footprint width on the orbit of the client satellite, which is in turn dependent on the antenna system and number of satellites in the constellation. A target intersection occurrence is once per client satellite orbit. 2.3.2Communication power: The system must work even if the client satellite has limited communication power. Worst-case client for this parameter is defined as a standard 1-U CubeSat. 2.3.3 Data capacity: Data transferred during a single target intersection occurrence depends on the mean intersection duration and the data rate. The duration depends on the width/area of the communication footprint, which in turn is dependent on the antenna system beam width. A transfer rate of 4800bps will allow for a telemetry packet of about 35kb given a 60-second communication window. 2.3.4 Target orbits: The constellation must supply this service to satellites in orbits ranging from 300km to 800km altitude. Figure 2(c): Antenna coverage on different orbits
  • 10. 10 2.4 Orbit/Constellation Description: The orbit design of the system consists of calculating the orbital parameters (inclination, eccentricity and semi-major axis) and determining the amount of satellites needed for the constellation. An equatorial orbit is chosen to ensure that the satellites will pass a ground station, which will be situated as close as possible to the equator, at least once per orbit. Any other orbit would cause the satellite to drift away from the ground station because of the rotation of the earth. The long latency between communication opportunities between satellites in more inclined orbits (e.g. polar and sun-synchronous) and their ground stations is the problem that our system will improve upon. With the proposed system, client satellites will cross our constellation twice per orbit. There exist areas, at different altitudes, where satellites can slip through without being able to communicate with the constellation. These areas are illustrated in Figure 3. However, client satellites would never pass through these areas more than once per orbit, ensuring communication at least once per orbit. A passing client satellite will have access time to a satellite in the constellation, which depends on the area of the antenna‘s beam on the orbital plane of the client satellite. The access time is also influenced by the inclination of the client satellite, which would determine the relative velocities of the two satellites. The system is simulated in MATLAB with the OuterNet at 900 km altitude and the client satellites at various altitudes and inclinations. The resulting average access times are shown in Figure 4. The altitude of 900 km was chosen in order to service a wide range of client satellites at altitudes ranging from 300-800 km, while also keeping the aerodynamic drag force at a minimum. Less drag force results in less orbital station keeping required and therefore less fuel required. Inter-satellite communication can also be considered in the future to minimise the latency between client satellites and a ground station. A message sent from a client satellite to the constellation could then be relayed around the constellation to a constellation satellite that is above (or close to) a ground station, allowing a message to reach earth within minutes.
  • 11. 11 2.5 Space Segment Description: 2.5.1 Link budget: A pointed VHF dipole antenna and a UHF patch antenna array will be used to communicate with client satellites, while an omni-directional dipole will be used to communicate with the ground station. Link budgets were calculated using the UHF downlink / VHF uplink Full Duplex Transceiver as a worst case client transceiver. The transmitted power of this module is only 150mW. Table 1 shows preliminary parameters of the link budgets with the client satellite and with a ground station. Table 1: Link Budget 2.5.2 For QPSK modulation Space Mission Analysis and Design: The required OuterNet satellite antenna gains and required power were calculated using the following link equation:
  • 12. 12 From this analysis it can be seen that the client downlink will require the most power and highest satellite antenna gain, justifying the use of a patch antenna array. The antennas will have a beam width of 60o per antenna spaced out by 22o, producing the pattern shown in Figure 5. Simulation using STK showed that a client satellite with a 600km sun synchronous orbit, gave an average access time of 60 seconds, allowing 35kb data per orbit to be transferred at 4800bps. A pass through the constellations orbit without coverage happened 2 times in 41 passes, and never sequentially. The range limitation was chosen to reduce LFS so that antenna gains would be realizable, while still providing good coverage across the equator. The VHF losses proved to be low enough to allow the use of a low gain dipole antenna. Communication between an OuterNet satellite and a client satellite will be initiated with an ID, sent out by the nearest OuterNet satellite. When the client receives its unique ID, communication between the OuterNet satellite and client satellite will commence. The modulation technique and protocol of the communication system on the OuterNet satellites will be software programmable, in order to accommodate as many client satellites as possible. 2.5.3 Antenna Design: The key performance parameters identify the need for a lot of attention to be given to the design of the antenna system. An antenna beam width of at least 150° in the one direction and 60° in the other direction, as well as sufficient gain, need to be achieved. The use of patch antennas will be preferred above other antennas due to their thin package form. Different patch antennas for different frequencies can be stacked on top of one another to minimise the area required [9]. Initial design points to the use of three patch antennas with a relative angle to produce the 150° beam width. The VHF-band (145MHz) requires a very large patch. Calculations show a patch of minimum length 0.32m, described by: with the speed of light, 0 the resonance frequency, and the effective dielectric constant [10]. Ceramic has an effective dielectric constant of ≈10. The antenna design thus becomes unpractical. A dipole array will probably be used for the VHF-band and patch antennas for the UHF and S-band. Consultation with experts on antenna design confirmed that the antenna
  • 13. 13 specifications are feasible with an antenna array. The final antenna design will be shown in the final document. Figure 2(d): Antenna coverage pattern 2.5.4 Attitude Determination and Control System: The satellites in the constellation will only require pointing the S-band antennas to nadir. A control system is still required to de-tumble the satellite after launch and to keep the satellite 3-axis stabilised at nadir pointing. The proposed altitude of 900km is a bit far for gradient stabilisation and complete magnetic control. The initial ADCS will make use of magnetic de-tumbling and reaction wheels to get 5° pointing accuracy. The sensors to be used are a magnetometer, nadir- and coarse sun sensor combination for the determination of attitude. This can be easily realised using existing off the shelf products to reduce the required development time for these sensors. 2.5.5 Phasing: When the launcher reaches the desired orbit, all the satellites will be released at roughly the same point in the orbit. To achieve the desired ≈25 degree spacing between each satellite, cold gas (butane) thrusters system (Isp of ≈ 70) will need to be designed or bought and intergrated to allow each satellite to enter and exit a phasing orbit. The satellite would need two thruster burns: one at the start of phasing and one at the end of phasing. An example system using this technique is SNAP-1 from SSTL [11]. The phasing of the satellites can confidently be achieved with a cold-gas-thrusters system without adding too much complexity to the satellite design. The thrusters will also allow for the capability to deorbit the satellite at end of life.
  • 14. 14 Chapter-3 WHAT IS CUBESAT? 3.1 Introduction: A CubeSat is a type of miniaturized satellite for space research that usually has a volume of exactly one liter (10 cm cube), has a mass of no more than 1.33 kilograms and typically uses commercial off-the-shelf components for its electronics. Beginning in 1999, California Polytechnic State University (Cal Poly) and Stanford University developed the CubeSat specifications to help universities worldwide to perform space science and exploration. While the bulk of development and launches comes from academia, several companies build CubeSats such as large-satellite-maker Boeing, and several small companies. CubeSat projects have even been the subject of Kick starter campaigns. The CubeSat format is also popular with amateur radio satellite builders. Figure3(a):- Cubesat
  • 15. 15 3.2 Design of Cubesat: The CubeSat specification accomplishes several high-level goals. Simplification of the satellite's infrastructure makes it possible to design and produce a workable satellite at low cost. Encapsulation of the launcher–payload interface takes away the prohibitive amount of managerial work that would previously be required for mating a piggyback satellite with its launcher. Unification among payloads and launchers enables quick exchanges of payloads and utilization of launch opportunities on short notice. The term "CubeSat" was coined to denote nano-satellites that adhere to the standards described in the CubeSat design specification. Cal Poly published the standard in an effort led by aerospace engineering professor Jordi Puig-Suari. Bob Twiggs, of the Department of Aeronautics & Astronautics at Stanford University, and currently a member of the space science faculty at Morehead State University in Kentucky, has contributed to the CubeSat community. His efforts have focused on CubeSats from educational institutions. The specification does not apply to other cube-like nano-satellites such as the NASA "MEPSI" nano-satellite, which is slightly larger than a CubeSat. In 2004, with their relatively small size, CubeSats could each be made and launched for an estimated $65,000–$80,000. This price tag, far lower than most satellite launches, has made CubeSat a viable option for schools and universities across the world. Because of this, a large number of universities and some companies and government organizations around the world are developing CubeSats — between 40 and 50 universities in 2004, Cal Poly reported. The standard 10×10×10 cm basic CubeSat is often called a "one unit" or "1U" CubeSat. CubeSats are scalable along only one axis, by 1U increments. CubeSats such as a "2U" CubeSat (20×10×10 cm) and a "3U" CubeSat (30×10×10 cm) have been both built and launched. In recent years larger CubeSat platforms have been proposed such as 12U (24x24x36 cm) to extend the capabilities of CubeSats beyond academic and technology validation applications and into more complex science and defense goals.
  • 16. 16 Figure3(b):- Design of a Cubesat Since CubeSats are all 10x10 cm (regardless of length) they can all be launched and deployed using a common deployment system. CubeSats are typically launched and deployed from a mechanism called a Poly-PicoSatellite Orbital Deployer (P-POD), also developed and built by Cal Poly. P-PODs are mounted to a launch vehicle and carry CubeSats into orbit and deploy them once the proper signal is received from the launch vehicle. P-PODs have deployed over 90% of all CubeSats launched to date (including un-successful launches), and 100% of all CubeSats launched since 2006. The P-POD Mk III has capacity for three 1U CubeSats, or other 1U, 2U, or 3U CubeSats combination up to a maximum volume of 3U. CubeSat forms a cost-effective independent means of getting a payload into orbit.[3] Most CubeSats carry one or two scientific instruments as their primary mission payload. Several companies and research institutes offer regular launch opportunities in clusters of several cubes. ISC Kosmotras and Eurokot are two companies that offer such services.
  • 17. 17 3.2.1 System Design: The CubeSat program, created at Stanford University‘s Space Systems Development Laboratory, provides logistics and launch services for 1-kg cube-shaped satellites measuring 10-cm on a side. CubeSats are deployed in groups of three from the Poly Picosatellite Orbital Deployer (P-POD), designed at CalPoly-San Louis Obispo. Launch is aboard a Russian Dnepr launch vehicle (converted from the SS-18 ballistic missile) from Baikonur Cosmodrome. A generic CubeSat-based platform capable of satisfying the basic requirements of LEO-based science missions was developed. This platform consists of all subsystems needed to support and power a small science instrument as well as communicate data to a ground station. Additionally, two separate science and attitude control subsystems were developed to accommodate the two science missions. 3.2.2 Internal and External Configuration: Figure 3(c) depicts the internal configuration of the CubeSat. The large toroid on the bottom face is the gravity gradient damper discussed in the Attitude Control section below. The damper surrounds the tether deployer in this figure; the boom mechanism used by the GPS mission also fits in this space. The communications, C&DH, and science cards used by the CubeSat are arranged in a stack parallel to the bottom face, and the batteries are enclosed in a separate box on the right side of the figure. Figure 3(c)- Internal Configuration
  • 18. 18 Figure 3(d) is a series of diagrams outlining the spacecraft‘s external configuration. The two missions have slightly different external configuration needs. Common external components include solar cells and a communications antenna, and both configurations provide access to an RJ45 Ethernet port and a kill switch as specified by the CubeSat program. The DC/PIP mission also incorporates two patch antennae for the science experiment, and the GPS mission includes a pair of redundant GPS antennae. Both missions have equal solar cell coverage. All components, with exception to the science packages, are off the shelf components and/or designed by the students. The primary qualification of these components will be through thermal vacuum and vibration testing on both the component and spacecraft level. Figure 3(d)- External Configuration 3.3 Power Supply to a Cubesat: Satellites in orbit mostly derive their power from the sun. This power is used to energize the satellite‘s systems which include the payload and all of the components that it needs to stay in orbit and function. Most satellites provide a very short window of time for a controlling station on earth to manage its internal problems and for user interaction with it. This is why the satellite needs to be an independent entity which can perform its own housekeeping and its own fault corrections. This is especially true in the management of power.
  • 19. 19 Systems in a satellite don‘t exactly work at the same time and also an option is needed from a user in an earth controlling station to be able to switch on or off these systems. Satellites in orbit are exposed to radiation particles from the sun, this radiation in turn induce and produce faults where a system drains too much power from its supply and overcurrent and overvoltage or other power-related conditions take place. Also, satellites, apart from the energy received from the sun need for a constant supply of energy when the satellite is on the shadow side of the earth where solar energy collection is at a minimum so a battery pack works along with the solar collectors in a way that the solar collectors can charge the battery while the batteries supply the system with the needed power and when the satellite is in shadow the batteries work alone to give the systems their needed power. From all of these requirements it is then known that it is necessary to have a self-sustainable and smart power supply. Eclipse Micropower Design‘s project is to develop a smart power supply that can switch the systems by itself either for necessity of use or because of a fault in the system. An On Board computer takes charge of receiving data from sensing circuits and a microcontroller to then switch on or off each individual system. As a future project proposal, this can also be done if a user from an earth controlling station receives a report from the satellite that such action is needed. Other options are available in the form of providing backup fuses for systems that use them, such as the On Board computer. The system would then have to endure and be protected from radiation in space, especially components having transistors and logic components and ways of dissipating radiation or retain some for heating as would be in some cases were the satellite, when in shadow is unable to keep a safe operating temperature for certain components. The system will also be able to protect itself against temperatures by using circuits which monitor temperatures in the various systems and are able to switch them on or off as needed.
  • 20. 20 3.4 Problem Definition: Most nanosatellite, picosatellite and cubesat missions fail due to problems with their power supplies. A satellite needs to accomplish its mission with very little or no human intervention and any overvoltage, undervoltage, overcurrent, undercurrent and temperature fluctuation conditions can render a satellite‘s systems useless. This is why a Smart power supply option is needed where it is able to deliver power to the mission-required systems and protect them should any problems arise. An intelligent power supply should be able to extend the life of a satellite and all its components and guarantee mission success. The designed system of the group is one such that it could be implemented by any client with a Cubesat mission, regardless of its particular mission or power needs. Some of the space environment variables that can affect a satellite‘s system are: 1.) Temperature extremes: from -40°C to 80°C. 2.) Heat in the form of radiation, not convection or conduction. 3.) Radiation bombardment that can affect components by leaving ―trails‖ of ionized particles and cause short circuits. Also gamma rays and solar wind particles can induce overvoltage or undercurrent conditions and damage systems. 3.5 Design Specifications: Eclipse Micropower‘s Design solution for the Cubesat power problem was to design a distribution system for the components of the Cubesat that monitors, detects and corrects faults in voltage and current as well as providing temperature monitoring. The group‘s intent was to design a protection scheme for a Cubesat Power Supply Unit that would be flexible, being able to be modified and used in any Cubesat mission or application. In order to make a Power Supply Unit that is smart, operates with or without human intervention and its capable of troubleshooting power issues on its own, the group has come up with a simple scheme consisting of the following parts: 1. A 8.2V DC BUS connected directly to a 8.2V DC battery array which feeds system their needed power.
  • 21. 21 2. A ―slave‖ microcontroller which acts as a protection for the systems, to switch on or off the systems as needed in the case of faults or simply by user demand and mission needs and provides this data to the OBC which can be sent as reports to an earth control station. 3. A sensing/ switching circuit at the input of the systems that provides the Microcontroller with voltage and current data. A current-to-voltage converter, (or transimpedance amplifier) is an electrical device that takes an electric current as in input signal and produces a corresponding voltage as an output signal. Three kinds of devices are used in electronics: generators (having only outputs), converters (having inputs and outputs) and loads (having only inputs). Most frequently, electronic devices use voltage as input/output quantity, as it generally requires less power consumption than using current, as it is the case with our Microcontroller. 4. DC/DC converters connected to the 8.2V DC BUS and to the input of the systems to provide and control the operating voltages needed for the systems. A simple DC/DC power converter or in electronics, a voltage divider (also known as a potential divider) is a simple linear circuit that produces an output voltage (Vout) that is a fraction of its input voltage (Vin). Voltage division refers to the partitioning of a voltage among the components of the divider. The equation to calculate output voltage is given by: Temperature sensing and switching of a warmer for batteries. Temperature sensors that would monitor the system‘s temperature, especially when the satellite is on the shadow side of the earth and they can activate coil-based heaters to maintain the systems at normal operating temperatures, especially the battery packs. They can also protect from overheating especially for the batteries and Microcontroller.
  • 22. 22 Our design is one where each system in the Cubesat is monitored using a sensing circuit. The Microcontroller has the minimum/maximum ratings of the system‘s voltages and currents programmed and if fed by the sensing circuit a parameter out of the predetermined values it can make the decision and switch off the system and then later turn it back on after a set time. 3.6 Purpose of using a Cubesat: The primary mission of the CubeSat Program is to provide access to space for small payloads. The primary responsibility of Cal Poly as a launch coordinator is to ensure the safety of the CubeSats and protect the launch vehicle (LV), primary payload, and other CubeSats. CubeSat developers should play an active role in ensuring the safety and success of CubeSat missions by implementing good engineering practice, testing, and verification of their systems. Failures of CubeSats, the P-POD, or interface hardware can damage the LV or a primary payload and put the entire CubeSat Program in jeopardy. As part of the CubeSat Community, all participants have an obligation to ensure safe operation of their systems and to meet the design and testing requirements outlined in this document. 3.7 P-POD Interface: The Poly Picosatellite Orbital Deployer (P-POD) is Cal Poly‘s standardized CubeSat deployment system. It is capable of carrying three standard CubeSats and serves as the interface between the CubeSats and LV. The P-POD is an aluminum, rectangular box with a door and a spring mechanism. CubeSats slide along a series of rails during ejection into orbit. CubeSats must be compatible with the P-POD to ensure safety and success of the mission, by meeting the requirements outlined in this document. Additional unforeseen compatibility issues will be addressed as they arise. 3.8 General Responsibilities: 1. CubeSats must not present any danger to neighboring CubeSats in the P-POD, the LV, or primary payloads: • All parts must remain attached to the CubeSats during launch, ejection and operation. No additional space debris may be created. • CubeSats must be designed to minimize jamming in the P-POD.
  • 23. 23 • Absolutely no pyrotechnics are allowed inside the CubeSat. 2. NASA approved materials should be used whenever possible to prevent contamination of other spacecraft during integration, testing, and launch. 3. The newest revision of the CubeSat Specification is always the official version • Developers are responsible for being aware of changes. • Changes will be made as infrequently as possible bearing launch provider requirements or widespread safety concerns within the community. • Cal Poly will send an update to the CubeSat mailing list upon any changes to the specification. • CubeSats using an older version of the specification may be exempt from implementing changes to the specification on a case-by-case basis. Cal Poly holds final approval of all CubeSat designs. Any deviations from the specification must be approved by Cal Poly launch personnel. Any CubeSat deemed a safety hazard by Cal Poly launch personnel may be pulled from the launch. 3.9 Dimensional and Mass Requirements: CubeSats are cube shaped picosatellites with a nominal length of 100 mm per side. Dimensions and features are outlined in the CubeSat Specification Drawing. General features of all CubeSats are: • Each single CubeSat may not exceed 1 kg mass. • Center of mass must be within 2 cm of its geometric center. • Double and triple configurations are possible. In this case allowable mass 2 kg or 3 kg respectively. Only the dimensions in the Z axis change (227 mm for doubles and 340.5 mm for triples). X and Y dimensions remain the same.
  • 24. 24 Figure 3(e): CubeSat isometric drawing. 3.10 Structural Requirements: The structure of the CubeSat must be strong enough to survive maximum loading defined in the testing requirements and cumulative loading of all required tests and launch. The CubeSat structure must be compatible with the P-POD. • Rails must be smooth and edges must be rounded to a minimum radius of 1 mm. • At least 75% (85.125 mm of a possible 113.5mm) of the rail must be in contact with the P-POD rails. 25% of the rails may be recessed and NO part of the rails may exceed the specification. • All rails must be hard anodized to prevent cold-welding, reduce wear, and provide electrical isolation between the CubeSats and the P-POD.
  • 25. 25 • Separation springs must be included at designated contact points (Attachment 1). Spring plungers are recommended. A custom separation system may be used, but must be approved by Cal Poly launch personnel. • The use of Aluminum 7075 or 6061-T6 is suggested for the main structure. If other materials are used, the thermal expansion must be similar to that of Aluminum 7075-T73 (P-POD material) and approved by Cal Poly launch personnel. • Deployables must be constrained by the CubeSat. The P-POD rails and walls are NOT to be used to constrain delpolyables. 3.11 Electrical Requirement: Electronic systems must be designed with the following safety features. • No electronics may be active during launch to prevent any electrical or RF interference with the launch vehicle and primary payloads. CubeSats with rechargeable batteries must be fully deactivated during launch or launch with discharged batteries. • One deployment switch is required (two are recommended) for each CubeSat. The deployment switch should be located at designated points (Attachment 1). • Developers who wish to perform testing and battery charging after integration must provide ground support equipment (GSE) that connects to the CubeSat through designated data ports (Attachment 1). • A remove before flight (RBF) pin is required to deactivate the CubeSats during integration outside the P-POD. The pin will be removed once the CubeSats are placed inside the P-POD. RBF pins must fit within the designated data ports (Attachment 1). RBF pins should not protrude more than 6.5 mm from the rails when fully inserted. 3.12 Operational Requirements: CubeSats must meet certain requirements pertaining to integration and operation to meet legal obligations and ensure safety of other CubeSats.
  • 26. 26 • CubeSats with rechargeable batteries must have the capability to receive a transmitter shutdown command, as per FCC regulation. • To allow adequate separation of CubeSats, antennas may be deployed 15 minutes after ejection from the P-POD (as detected by CubeSat deployment switches). Larger deployables such as booms and solar panels may be deployed 30 minutes after ejection from the P-POD. • CubeSats may enter low power transmit mode (LPTM) 15 minutes after ejection from the P- POD. LPTM is defined as short, periodic beacons from the CubeSat. CubeSats may activate all primary transmitters, or enter high power transmit mode (HPTM) 30 minutes after ejection from the P-POD. • Operators must obtain and provide documentation of proper licenses for use of frequencies. For amateur frequency use, this requires proof of frequency coordination by the International Amateur Radio Union (IARU). • Developers must obtain and provide documentation of approval of an orbital debris mitigation plan from the Federal Communications Commission (FCC). • Cal Poly will conduct a minimum of one fit check in which developer hardware will be inspected and integrated into the P-POD. A final fit check will be conducted prior to launch. The CubeSat Acceptance Checklist (CAC) will be used to verify compliance of the specification (Attachment 2). Additionally, periodic teleconferences, videoconferences, and progress reports may be required. 3.13 Testing Requirements: Testing must be performed to meet all launch provider requirements as well as any additional testing requirements deemed necessary to ensure the safety of the CubeSats and the P-POD. All flight hardware will undergo qualification and acceptance testing. The P-PODs will be tested in a similar fashion to ensure the safety and workmanship before integration with CubeSats. At the very minimum, all CubeSats will undergo the following tests.
  • 27. 27 • Random vibration testing at a level higher than the published launch vehicle envelope outlined in the MTP. • Thermal vacuum bakeout to ensure proper outgassing of components. The test cycle and duration will be outlined in the MTP. • Visual inspection of the CubeSat and measurement of critical areas as per the CubeSat Acceptance Checklist (CAC). 3.14 Qualification: All CubeSats must survive qualification testing as outlined in the Mission Test Plan (MTP) for their specific launch. The MTP can be found on the CubeSat website. Qualification testing will be performed at above launch levels at developer facilities. In some circumstances, Cal Poly can assist developers in finding testing facilities or provide testing for the developers. A fee may be associated with any tests performed by Cal Poly. CubeSats must NOT be disassembled or modified after qualification testing. Additional testing will be required if modifications or changes are made to the CubeSats after qualification. 3.15 Acceptance: After delivery and integration of the CubeSats, additional testing will be performed with the integrated system. This test assures proper integration of the CubeSats into the PPOD. Additionally, any unknown, harmful interactions between CubeSats may be discovered during acceptance testing. Cal Poly will coordinate and perform acceptance testing. No additional cost is associated with acceptance testing. After acceptance testing, developers may perform diagnostics through the designated P-POD diagnostic ports, and visual inspection of the system will be performed by Cal Poly launch personnel. The P-PODs will not be deintegrated at this point. If a CubeSat failure is discovered, a decision to deintegrate the P-POD will be made by the developers in that PPOD and Cal Poly based on safety concerns. The developer is responsible for any additional testing required due to corrective modifications to deintegrated CubeSats. 3.16 Future development: An example of one of the ELaNa satellites is the University of New Mexico's Space Plug-and-play Architecture (SPA) proof of concept flight for the Trailblazer
  • 28. 28 mission. Trailblazer is a 1U Cubesat to be launched in 2012 under the ELaNa four mission. KickSat is scheduled for launch in early 2014. The goal of the QB50 project is to use an international network of 50 CubeSats for multi-point, in-situ measurements in the lower thermosphere (90–350 km) and re-entry research. QB50 is an initiative of the Von Karman Institute and is funded by the European Union. Double-unit ("2-U") CubeSats (10x10x20 cm) are foreseen, with one unit (the 'functional' unit) providing the usual satellite functions and the other unit (the 'science' unit) accommodating a set of standardized sensors for lower thermosphere and re-entry research. 35 CubeSats are envisaged to be provided by universities in 19 European countries, 10 by universities in the US, 2 by universities in Canada and 3 by Japanese universities. 10 double or triple CubeSats are foreseen to serve for in- orbit technology demonstration of new space technologies. All 50 CubeSats will be launched together on a single launch vehicle. The launch is planned for mid-2015. The Request for Proposals (RFP) for the QB50 CubeSat was released on February 15, 2012.
  • 29. 29 Chapter-4 CONCLUSION Outernet is an ambitious project that seeks to create a global WI-FI network that would provide the entire population of the world with free access to the Internet. A group of american researchers is out to build a network of satelites that would provide Internet while at the same time protecting the users identity and data. The new network is thought of as a new version of short radiowaves or even a ―space torrent‖. There are more WiFi devices in the world than people, yet only 40% of the global population has access to the wealth of knowledge found on the Internet. The price of smartphones and tablets is dropping year after year, but the price of data in many parts of the world continues to be unaffordable for the majority of global citizens. In some places, such as rural areas and remote regions, cell towers and Internet cables simply don‘t exist. The primary objective of the Outernet is to bridge this global information divide. Offering continuously updated web content also bypasses censorship of the Internet in countries that restrict access to independent media. Additionally, Outernet will offer a humanitarian notification system during emergencies and two-way Internet-access for a small set of users. The latter feature will be reserved for individuals and organizations that are unable to access conventional communication networks due to natural disasters or man-made restrictions to the free-flow of information. Citizens from all over the world, through SMS and feature-phone apps, participate in building the information priority list. Users of Outernet‘s website also make suggestions for content to broadcast; lack of an Internet connection should not prevent anyone from learning about current events, trending topics, and innovative ideas. The project should start running simulations this year, and in 2015 the initator want to start the construction phase.
  • 30. 30 REFERENCES [1] NASA. (2010, September) Tracking and Data Relay Satellites (TDRS). [Online]. http://nssdc.gsfc.nasa.gov/multi/tdrs.html [2] CubeSatShop.com, CubeSat Summer Workshop at Small Sat Conference. [Online] Http://www.cubesatshop.com/index.php?page=shop.product_details&flypage=flypage.tpl&prod uct_id=11&category_id=5&option=com_virtuemart&Itemid=67 [3] Toorian, Armen et. Al, ―CubeSats as Responsive Satellites,‖ Paper no. AIAA-RS3 2005- 3001, AIAA 3rd Responsive Space Conference, Los Angeles, CA, 25-28 April 2005 [4] CubeSat Kit (Pumpkin, Inc., San Francisco, CA). http://www.cubesatkit.com
  • 31. 31 APENDIX-A LIST OF FIGURE FIGURE NO. FIGURE NAME PAGE NO. 1(a) Outernet Plan 4 2(a) Conceptual Illustration of Outernet 7 2(b) Interfacing Between System Segments 8 2(c) Antenna Coverage on Different Orbits 9 2(d) Antenna Coverage Pattern 13 3(a) Cubesat 14 3(b) Design of Cubesat 16 3(c) Internal Configuration 17 3(d) External Configuration 18 3(e) Cubesat Isometric Drawing 24