In 2021, we became part of a consortium creating a project for the precursor of a Polish Earth observation satellite constellation. In cooperation with the Military University of Technology, Space Research Centre of the Polish Academy of Science, Lukasiewicz Institute of Aviation, Creotech Instruments S.A. and PCO S.A. within the program SZAFIR we started working on the creation of Polish dual- use satellites. In the project, we are responsible for the optical payload – 2 of 3 high-resolution Earth Observation telescopes that will provide information to support Polish defense and government.
Space conditions, including vacuum, very low temperatures, radiation, and strong UV radiation, negatively affect electronics, optical and mechanical equipment. Therefore, payloads placed on satellites should be designed and developed in such a way that makes it possible for those devices to work without interference. The best way to properly prepare the hardware is to continually test it in space-like conditions. There are several ways to do it: performing complex computer simulations including many parameters, testing in a vacuum chamber, or testing the equipment in the stratosphere. At Scanway Space, we have chosen the latter option.
The goal of such missions is to verify in space-like conditions the behavior of optical, mechanical, and electronic components that we are planning to place in orbit. The idea is to place the components developed and used by our engineers in the gondola of a stratospheric balloon, which ultimately reaches an altitude of 30 km in order to achieve low pressure and low-temperature conditions.
A mission usually consists of several experiments, for example, a test of optical coatings used in telescopes, a test of the OBC computer at low temperatures, and a test of components of the satellite mission self-diagnostic system.
The mission starts with the preparation of the balloon components, planning the experiments, creating the appropriate software to diagnose the equipment being tested. The next step is the balloon launch: the stratospheric balloon is filled with hydrogen (or alternatively: helium). Then, a payload is attached to the balloon containing the planned experiments. When all the steps are done correctly, the balloon is launched into the air.
After the balloon reaches the planned height (usually 35 km), it explodes and the controlled descent begins. During the whole mission, the onboard computer collects data, on the basis of which we are able to analyze the course of the mission and the behavior of all the payload elements.
This kind of stratospheric balloon flight cannot take place without obtaining the appropriate permissions, which are given by air navigation. Our missions are piloted by WroSpace Association.
Developing devices that are designed to work in space is a number of responsible and narrow-ranging activities. What is important in the mechanical aspect of designing a satellite? The mechanical design of a telescope must accomplish a mass of requirements. From the basics, allowing the satellite to survive the journey into space and later stages of the mission unscathed, to advanced, perfectly designed tools to ensure the safety of the mission and its trouble-free progress.
In designing the mechanics of the ScanSAT telescope, we placed great value on identifying and realizing safety and structural requirements. We divided them into functional and endurance aspects. Functional aspects are those that allow ensuring proper work of the imaging system. These include the mechanical structure - which must be designed in such a way that thermal deformation of the optical system does not affect the quality of imaging. The strength aspects, on the other hand, when used properly, protect the satellite from the effects of loads, accelerations, and vibrations. We also had in mind other mechanical components not related to security or imaging support, which must also pass durability tests and compatibility with the launch platform.
As a result, we developed an athermal optomechanical system that is constructed using, among other things, aluminum and carbon fiber composites. Resistance to temperature fluctuations is a very important feature here since it allows to minimize the influence of temperature fluctuations during the transition between the lit and the shaded part of the orbit. The application of this type of solution was possible to achieve only thanks to modern techniques of design support and numerical analysis.
What if things in space broke down as often as our microwave, washing machine, or robot on a processing line in a factory?
Not-so-good things would happen, and this is best illustrated with a data example. In 2019, approximately 13 million microwaves were sold in the U.S., requiring replacement every 7-10 years on average, and 10 million washing machines replaced every 10 years on average. By analogy, in space: one of the world's industry leaders Satellogic has only sent 21 satellites in its entire history (or as many as), and Maxar has sent 4.
In case of home appliances failure, we lose some money and a lot of comfort. In the case of space products, we lose a huge amount of money and data, in addition to that - non-functioning space objects remain in space (no replacement available) and turn into nothing more than space trash, creating a serious hazard. Seeing the obvious difference in the level of loss, it is worth considering - how to prevent big space problems?
The most complicated thing for space hardware is the launch itself. Sending anything even into LEO is associated with years of preparation and huge amounts of money - and that's basically what it is. The second and no less complicated thing is space itself. Gravity, vacuum, temperature, radiation - conditions definitely different from those on Earth. For example, all equipment sent into space should be adapted to work in a temperature range from -100 to 100 degrees Celsius.
Is space the most challenging environment for which humans build machines? No. There are places on Earth where conditions are even less friendly. For example, the ocean floor, where we struggle with pressures that require very advanced engineering solutions. Therefore, what is the most important in space projects is a new, open view. On the project itself, on the requirements, on instrumentation tests, on software, and even on the way of managing the project. Space challenges every obviousness and acting "by heart", regardless of the stage of the project, is usually harmful.
Statistically, most failures appear during the first year of equipment presence in space. The causes are varied: electronic, mechanical, soft. About 17% of the causes are failures defined as "unidentified". Since the space industry is not a place to learn from mistakes, the most important part of any space project are (or at least should be) requirements and testing.
The requirements (functional, performance, or design) are largely formed by the conditions in which the device will work. Space itself dictates a lot of them, and we should also add those defined by the nature of the payload. So it is not difficult to imagine a list of requirements for a satellite that is several full pages long - and that is, among other things: a sign of a well-recognized environment and clearly defined requirements. Fortunately, we can count on support in the field of defining and verifying requirements. Our space project will be taken care of by, among other things: external reviewers who will regularly review and redefine the predefined requirements.
But listing requirements is not the key to accomplishing them. They need to be constantly verified - in tests, checks, trials, and inspections. Such "training" not only allows you to note errors and learn as the project progresses - but it also provides a sense of order, eliminates many fears, and allows for comprehensive risk management. Testing is almost the most important part of creating any space project. No matter how many times we test a given element - there will always be not enough. No matter how many scenarios we consider, something may happen that we were not able to predict. The universe still knows how to surprise us, but the most important thing is to surprise us in what we couldn't predict despite our efforts.
The work of any device in space, including Earth observation satellites, requires the transmission of data to receiving stations. How do you send gigabits of information quickly? What if the data is sensitive and there is a need to secure the entire communication process? These and other problems are solved by laser telecommunication. As part of our research work, we decided to design and develop laser communication that would transmit data quickly and over very long distances, while ensuring their security.
Traditional radio communication is accomplished by appropriately modulating an electromagnetic wave that propagates in every direction and ultimately provides coverage of a very large area of the Earth. Laser communication works similar to fiber optic communication - from point A to point B. The photons entering the fiber from the transmitter go only to the destination point at the end of the medium (fiber) - the receiver. For space applications, the laser beam uses the atmosphere as a medium, but a properly prepared laser telecommunications module is able to send the beam to a specific, relatively small point on Earth. Conventional transmission of information carries a number of risks, such as frequency limitations, the need for an extensive network of receiving stations, encryption, low bandwidth, and constant upgrades to increase transmission power. Laser telecommunications solves these problems.
With laser communication, there is no need to regulate the legal process of information exchange due to the fact that the laser beam falls on a specific location on Earth. This enables a secure way of transmitting information where eavesdropping is only possible if the listener is physically next to the receiver. Due to the very high energy concentration, the transmission power is also much lower than in conventional telecommunications. The biggest advantage of laser telecommunications is its enormous throughput. Speeds of the order of gigabits per second are possible - values an order of magnitude higher than those used with conventional X-band or other telecommunications.
First of all, light is a physical phenomenon and has a dual nature. On the one hand, it is a stream of photons (the smallest energy carriers) that move in a specific direction, while on the other hand, it is a wave. For this reason, the nature of light is described as wave-particle duality, which gives the light a unique range of parameters.
We deal with light in practically every aspect of our lives. Natural and artificial light follows us all the time. Laser, ultraviolet, microwave, and X-ray light can be found everywhere. The most common parameters of light are luminous flux, luminous intensity, and luminance.
However, when looking at light scientifically, the most important parameters for classifying types of light are the wavelength [nm] emitted by the source, the frequency [Hz], and the irradiance [W/m2], which is the radiant flux per unit area.
Electromagnetic radiation by wavelength can be divided into:
There are 4 types of infrared radiation: NIR (Near Infrared), SWIR (Short-Wave InfraRed), MWIR (Mid-Wave InfraRed), and LWIR (Long-Wave InfraRed).
How do we measure with light in space? First of all, it is important to make a difference between Space Observations (stars, planets, meteoroids, etc.) and Earth Observations. For Earth Observations (EO), the mechanics of the measurement includes 3 steps:
Detectors of what type of radiation do we use for measurements in space? Waves of the visible VIS and infrared NIR and SWIR spectrums are most often registered. Photons of these types of radiation are either reflected or absorbed by objects on Earth, which allows achieving strong contrast necessary for high-resolution imaging. VIS is primarily used to identify an object, its shape, and its dimensions. However, infrared radiation gives other possibilities. One of them is to obtain the vegetation index NDVI which is calculated on the basis of NIR and VIS and allows defining the area as built-up area, uncovered land, water, snow, area with existing vegetation along with the type of vegetation.