Components, Electronics & Scientific Guide

Low Earth Orbit Satellite Communication

With small satellites in the LEO (Low Earth Orbit), a new wave of innovation in the space industry is emerging. The article takes a look at the emerging market for small satellite constellations and shows the difference between conventional radiation-resistant components and new plastic ICs. The OTA technology is using this same method.

Those who have been involved with the space industry lately have seen many new activities. With missions to Mars, Jupiter, asteroids and innovations in satellite and carrier rocket technology, the space industry is back in the headlines. Since the space exploration began in 1957 with Sputnik and the first manned space flight in 1961, there has not been as much public interest and enthusiasm in the industry as it is today. Fifty years later, with small satellites in the LEO (Low Earth Orbit), a new wave of innovation is emerging that will bring every dweller access to WiFi and mobile communications.

These activities had attracted the attention of venture capital firms and investors who have never before had anything to do with the space industry. The first launches of a few hundred small satellites were only moderately successful, creating a fragmented market. Missions ranged from elementary school projects and scientific experiments through technical feasibility studies to real-time Earth imaging.

However, all of this is changing with the development of large constellations consisting of small satellites and the focused efforts of conventional satellite manufacturers to provide broadband Internet connections anywhere in the world. Large semiconductor manufacturers are actively working on how to cover this new custom field with sophisticated concepts and innovative business models. The article takes a closer look at this emerging market for small satellite constellations and explains why manufacturers are refraining from the traditional radiation-resistant components used in aerospace over the past 50 years. Also, the article discusses

GEO and LEO satellites in comparison

Diversification is increasing in the satellite industry. Conventional satellites usually have an extended mission life (15 to 20 years) and are designed for a wide variety of orbits, such as geostationary orbit (GEO), and space. They are designed for high radiation levels and must meet the strictest reliability and quality requirements. In contrast, small satellites in the LEO move below the Van Allen radiation belt, shielding most destructive particles. For these satellites, the requirements for radiation resistance, reliability, and quality are lower. Hundreds of small interconnected satellites forming an LEO constellation network.

The massive gap between these two basic satellite classes is increasingly diminishing. Future large constellations planned for the higher LEO as well as greater satellite functionality will lower operating costs. This requires more satellites with slightly longer mission lifetimes (about five years), higher orbits (1100 to 1300 km), higher radiation demands, and stricter reliability and quality requirements.

Challenge in using COTS

Because these large constellations have more demanding technical requirements than previous small satellites, this also affects the IC numbers. Although the electronic functionality per satellite is lower than that of larger, more traditional satellites, the sheer number of small satellites and ground stations is associated with a significantly higher volume potential per product. Such possibility has never existed and can be expected lower component costs. Even if the demands on technology or radiation exposure are less stringent than with conventional satellites, the challenges of large constellations are still associated with considerable costs and risks.

To reduce costs, the trend is towards commercial COTS components, which cost considerably less than conventional radiation-resistant components. For this purpose, a test plan is set up, tests are performed and results are collected and analyzed. In most cases, the cost of outsourced radiation testing and electrical shielding add up quickly because most IC manufacturers do not have the necessary facilities to perform such work internally. The amount of workforce involved in creating a test plan, implementing it, and analyzing the data collected is significant because it consists of a learning curve: understanding the component under test, and tackling problems with test setup and handling unexpected test results.

Ultimately, the risk regarding program cost and a schedule is high if the IC does not deliver the results required by the program, or if there is a potential for significant production variability in the production release. How can the requirements regarding technology, radiation exposure and differentiation characteristics from the competitor be met by commercial performance – and at the same time keep the costs within reasonable limits?

Since the performance of the electrical system of a given satellite is based on the selected components, the component manufacturer should work to solve the described challenges. The manufacturer has designed the innovative features of its ICs and knows best about its parts and their underlying technology. Even if this makes sense in theory, many component manufacturers focus on other high volume businesses despite the potential for higher volumes. They are reluctant to support this particular customer base fully, or simply do not have the necessary know-how. Some IC manufacturers, for example, do not know whether their component meets the required radiation exposure requirements – or whether it could meet these requirements.

Radiation-resistant IC production process

Companies with the proper understanding, skills and experience to support the small satellite marketplace strive to understand and engage in this fragmented market without having to change their business model fundamentally. There is no clearly defined set of specifications or quality standards in the industry that could serve as a common denominator for the relevant suppliers. However, in the industry, this area has again become increasingly in focus in recent years. Renesas Electronics is frequently engaged in this market segment, given the new requirements and convergence of elements for larger satellite constellations in the higher LEO. Renesas, therefore, has a cost-effective, radiation-resistant product development and manufacturing process developed for the requirements of these small satellites. As a result, the company presents a family of products in compact SMT plastic packages with nickel/ palladium/gold (Ni / Pd / Au) lead finish.

These ICs are uniquely developed in the development of a Total Ionizing Dose (TID) of up to 30 krad (Si), for Single Event Effects (SEE) with a linear energy transfer (LET) of up to 43 MeV and a military operating temperature range of -55 ° C to +125 ° C. The components also receive an AEC-Q100-compliant qualification with burn-in tests of up to 2000 hours, 500 temperature cycles, and package moisture sensitivity tests. This development and manufacturing process differs significantly from that of traditional radiation-resistant products: these have large ceramic packages and undergo radiation protection testing, temperature and burn-in testing in production, which translates into IC cost. Applications of Cloud Computing in Healthcare is another issue connected with it.

Avoid catastrophic SEEs

The likelihood of single-event effects and the associated potential energy level of such an event or particle is likely to be lower on an LEO than on a GEO, but for a large satellite constellation at a height close to or in the Van Allen Belt still questionable. For ICs with an extensive digital range of functions, such as a microprocessor, an SEE is usually not a catastrophic event. The problem can often be solved by switching the supply voltage off or on, or software-based corrections. Perhaps this is entirely different with a device that supplies the microprocessor or processes the sensor data signals for the microprocessor.

Depending on the manufacturing process, the device may have some degree of stability against a destructive event at a particular rated voltage. But it will be particularly attractive for a single-event transient (SET) or a SEFI (single-event functional interrupt). If a heavy ion or particle hits a power electronics module or operational amplifier in such a way that its output signal is undesirably disturbed during a transient event, it may potentially damage or destroy a device (such as a microprocessor) connected to its output. In some instances, this can mean the loss of a mission or the entire satellite.

In the best case, an interruption of the output signal occurs, which makes it necessary to switch the supply voltage off and on again, which causes a malfunction of the corresponding satellite section. In the IC concerned, such events can only be remedied by measures in IC design. To address this challenge, there are system-level techniques. These may increase the system complexity of the plan, the production implementation, the analysis, manufacturing or procurement, which in turn increases satellite or program costs. Furthermore, they can increase the dimensions, weight and energy requirements of the system solution, which directly precludes the goals of a smaller satellite with higher performance at a lower cost.

A new class of radiation-resistant ICs

Renesas introduces the first three radiation-resistant ICs in its proprietary plastic packaging: the ISL71026M 3.3V CAN (Controller Area Network) transceiver, the ISL71444M 40V Quad-Precision RRIO operational amplifier (Rail-to-Rail Input-and-Output ) and the ISL71001M 6 A POL voltage regulator (point-of-load). The ISL71026M and ISL71444M are available in a TSSOP SMT package; the ISL71001M comes in an SMT QFP. All of these devices have a Ni / Pd / Au lead finish to prevent the formation of tin whiskers.

These building blocks are just as powerful as commercial components. They provide decent housings and radiation resistance for cost-effective satellite constellation programs while minimizing risk, for example, the bad SET behavior of the quadruple operational amplifier ISL71444M with output settling times below 3 μs and a LET of 43 MeV × cm 2 / mg after a massive ion impact. When using this operational amplifier, the user does not have to deal with system-level improvements.

Renesas has been active in the satellite industry for more than 50 years, so the company understands the importance of long-term delivery continuity and takes every opportunity to make sure a product does not become obsolete. In sporadic cases, a comprehensive end-of-life sourcing program is offered. In addition to plans for large satellite constellations, these products are also ideal for other applications such as launcher, medical equipment, avionics for high altitudes and nuclear power plants.

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