My little satellite…

How far can the trend of downsizing satellites be promoted and is there a price for downsizing the satellite? About nanosatellites and their place in space exploration today and in the future

Tal Inbar, published in Galileo - April 2008

Satellites, moving in their orbits around the earth for 51 years, are considered extremely complex devices. Satellites are equipped with various systems that allow them to perform their tasks: power source, computer, control systems, propulsion systems, cameras, communication equipment, temperature control equipment - and this is of course only a very partial list.

For years it seemed that satellites would always be big, heavy and expensive. With the development of the miniaturization of electronic components, primarily computer processors, the satellites (in part) began to "shrink". The miniaturization of certain satellites opened the way for more frequent space missions, at lower costs, and for the use of smaller and weaker satellite launchers - which also lowered the overall cost of the space mission.

How far can the trend of downsizing satellites be promoted? Is there a price for reducing the satellite? Here we will present the field of tiny satellites, often referred to as nanosatellites, and see what their place is in space exploration today and what possible applications they can fit in the future.

mini-micro-nano

The division into sizes of satellites varies, and depends on the definer. Some divide satellites into sizes according to weight, some do so according to the cost of the mission. Despite the differences, the common and accepted definition in the world space community is this:

• A large satellite - weighing over 1,000 kg
• Medium satellite - weighs between 500 kg and 1,000 kg
• Mini-satellite - weighs between 100 kg and 500 kg
• Micro-satellite - weighs between 10 kg and 100 kg
• Nano-satellite - weighs between 1 kg and 10 kg
• Pico-satellite - its weight is between 100 grams and 1 kg
• Femto-satellite - weighs less than 100 grams

It must be remembered that this division is not an inviolable law, and that different satellites are defined differently by their developers. Here we will concentrate on nanosatellites.

The story of the CubeSat

Cubesat (Cubesat) is a general name for a tiny satellite platform, developed in collaboration between Stanford University and the California Polytechnic Institute, as an innovative method that will allow students to launch a satellite quickly and cheaply. The configuration of the basic satellite in this family is a cube, whose edge is 10 cm long.

The first CubeSat satellite was launched at the cost of a student satellite - only tens of thousands of dollars. At the beginning of the use of CubeSat satellites, the satellites themselves, based on their content, were built by those who desired it, according to plans provided to them. Today, it is much more common to use a pre-prepared satellite kit, sold in a variety of sizes and designs. In fact, the CubeSat design created standardization in the field of tiny satellites, as the absolute majority of these satellites are based on the CubeSat platform.

Cubesat satellites are launched using a generic launcher, a sort of box into which up to three satellites are inserted at once. When the launcher reached space, the case opened and a spring pushed the satellites out into space. As a general rule, nanosatellites - and cubesats in them - are not launched as a dedicated and unique payload, but as an accompanying payload for various launches around the world. A significant part of CubeSat satellite launches so far has been carried out using the Russian Dnieper satellite launcher. Additional launches were carried out using the Russian Cosmos 3 launcher. India also allows these satellites to be launched into space with the PSLV rocket (which was used in January 2008 to launch the Israeli Texar radar satellite).
Increasing accessibility to space

The intention of the CubeSat platform developers was to lower the price of the satellite vehicle to a minimum, and to exempt those interested in launching a tiny research satellite from the need to design the body of the satellite and part of its operating system, which currently comes with the body. Dozens of CubeSat satellites have been launched into space so far, and dozens more projects are in various stages of planning. Increasing accessibility to space on the one hand, and the low price of a satellite project on the other hand, enable the implementation of educational and research initiatives and access to space for developing countries, which would not have been able to launch a satellite into space in other ways.

Using off-the-shelf components for space applications in general - and for nanosatellites in particular

In general, the world's space industries are extremely conservative regarding the components and systems integrated into satellites. Nevertheless, the use of off-the-shelf components (COTS, Commercial off the Shelf) in the field of space is slowly becoming not only a reality, but almost a necessity, due to the large costs (in money, time and personnel) of the alternatives.

The American Air Force noted, in a document from 2006, the advantages of off-the-shelf technologies in the field of space - shortening the development times of the individual components; Simplicity and speed in the development of space systems based on standards; Reducing the cost of testing, due to the use of standard network testing tools and remote access; Faster software development, based on existing modules; reducing the manpower needed to operate a satellite; and sharing communication assets between different space platforms.

The accessibility of kits for building tiny satellites, and especially the CubeSat kit, makes the cost component of the satellite chassis marginal - something that allows the bulk of the budget to be directed to MET.

The big disadvantage is the lack of redundancy

Since satellites operate in extremely difficult environmental conditions (temperature range of hundreds of degrees Celsius, radiation, strong magnetic field) and it is usually impossible to provide them with repair and maintenance services, various backup systems are built in them, which allow redundancy - that is, the continued functioning of the satellite in a normal manner even if A failure occurs in the main system.

In many satellites the balance is full, and usually it is double. In some systems, the balance is even triple. The biggest disadvantage of tiny satellites is the almost complete lack of reserves, for a simple reason - there is no room for it in a satellite. Among the exceptions is the tiny Israeli satellite ISAT-1, in which all its systems are fully operational.

Structure flights and satellite swarms

Tiny satellites have been tested in the last decade as candidates for structure flights in space, that is, a flight of two or more satellites while maintaining a mutual position in space and changes in the geometric configuration of the structure. Future satellite swarms, which could contain tens or hundreds of tiny satellites, could have multiple uses in research, such as in the search for gravitational waves, in astronomical research, in rapid survey of planets and moons, and in military missions.

Among the challenges facing the developers of the satellite swarm idea, we can mention the structure management system, the means of control and control of each satellite and its communication system with other satellites, the need to avoid collision with other objects in space - and this is only a partial list. The development of algorithms required for building flights in space is carried out, among other things, at the Asher Institute for Space Research at the Technion. A swarm of tiny satellites will include many satellites with low reserves, but the total reserves of the swarm will be high - the normal satellites will be able to perform the tasks of broken satellites, without harming the mission for which they were launched into space.

"Blue and White" nanosatellites

Israel is on the nano-satellite map, and two satellites are currently being built there, which are in the phase of integrating the satellite parts (integration) at the Aerospace Industry's space plant facilities. The satellites were designed by the experts of the Israeli Nano Satellite Association (INSA), which was founded in 2006 by a group of space engineers from Israel's various space industries.

The first Israeli nanosatellite, known as ISAT-1, will be used to prove the function of satellite components under real conditions - that is, in space. As mentioned, the satellite industry is extremely conservative, mainly because it is impossible to repair components that have malfunctioned in space and due to the enormous cost of satellite projects. Therefore, components that we use in everyday life, such as Pentium processors, have not yet reached space, simply because no manufacturer wants to risk launching a component that has not yet been tested in space.

The use of nano-satellites makes it possible to break this vicious circle, and to put tiny laboratories into space that examine the behavior of new components in space. One of the main bottlenecks in the space industry is proving the operation of components and systems designed for installation in satellites - a long and expensive process, which is carried out in only a few laboratories around the world (in Israel, a highly advanced laboratory for imaging space environments operates in the Sorek Nuclear Research Center complex).

A satellite for proving space components is designed to test the components in space conditions while integrating them into a tiny satellite platform. The process will be faster and cheaper than exams in laboratories, and its great advantage is the creation of heritage, a space heritage, i.e. a demonstration that certain components work and have worked in space. This is a kind of "kosher seal" of the components and systems. The association's first satellite is expected to be launched into space in the first half of 2009, using the Dnieper satellite launcher.

Ben-Gurion University is also engaged in nanosatellite development, and has already bought several kits for building a satellite from the American company Pumpkin. Technical details about the satellite, or a planned date for its launch, have not been published so far.

The students of Handasaim High School-Herzliya studied the subject of tiny satellites under the leadership of Dr. Anna Heller. As part of the studies, the students dealt with various aspects of planning a ground station to receive satellite broadcasts, in the characterization of a tiny satellite and in carrying out research work on satellite systems. A model of the satellite developed in high school was presented at the Ilan Ramon International Space Conference in 2007.

A small satellite laboratory is currently being established in Herzliya. As part of the laboratory, the city's students, who will study in a unique curriculum, will design and build a nano-satellite that will be launched into space within about 3 years. The Minister of Science, Culture and Sports, Galeb Majadala, was impressed by the project and announced that his office would support it and even encourage outstanding Arab students in the sciences to take part in the project.

The launch stages of the ISAT-1 satellite

Possible applications

The variety of possible applications for nanosatellites is enormous. However, it must be remembered: a nanosatellite is not usually a substitute for a larger satellite. The importance of photography and communication satellites will not diminish despite the operation of the nanosatellites. Nanosatellites can be used for a variety of scientific tasks, for proving technologies, for protecting space assets, for space advertising, for demonstrating innovative technologies, and more. One of the interesting applications, which can be a fertile ground for the use of nanosatellites, is placing these tiny satellites as sentinels, to protect essential space assets such as photography or communication satellites.

More on tiny satellites

• Cubesat satellite user community
• The site of the Pumpkin company, a manufacturer of tiny satellite kits
• The website of the Israeli Association for Small Satellites

When a threat approaches the satellite, in the form of a space weapon of some kind, a tiny satellite will be able to move into a collision course with the threat, thus protecting the large satellite. These tiny satellites could be placed around the satellite and at some distance from it, or be integrated in dedicated niches inside the satellite. Such a combination will even allow them to receive electricity from it for their operation.