Space: A Continually Evolving Frontier

For decades, satellites have been used in a variety of applications including Earth observance, communications, military, GPS, weather forecasting, space telescopes and remote sensing. The rapid progress made in space technology led to such notable accomplishments as the Moon Landing. In the past few years, there has been an acceleration of space systems aiming to expand high speed global connectivity powered by low Earth orbit (LEO) satellite and Geostationary Orbit Satellite (GEO) constellations. The era of “New Space” has arrived with a growing number of companies offering global low latency broadband internet services using LEO constellations comprised of thousands of satellites.  

Beyond broadband internet, other applications for these LEO constellations are being developed to support the growing desire for persistent situational awareness, allowing real-time monitoring of natural disasters, impacts of climate change and many military-driven scenarios using high-resolution earth observation and synthetic aperture radar (SAR). The number of satellites in LEO has increased by 50% in the last two years alone. Another segment in new space is low-cost CubeSats, shown in Figure 1. 

Figure 1: Structure of ESTCube Cubesat

These small form factor low-cost satellites have attracted a new set of entrants such as universities and schools, enabling the creation of startups and spinoffs alike. All the above systems are driving the need for new smaller but high-performance and data-intensive electronics. Size, Weight and Power (SWaP) is a significant factor in space applications primarily because of launch costs, the impact of weight on fuel requirements, and both volume and weight with regard to shipping and storage costs. Thus, the more compact and lightweight the component, the better. 

As satellite service providers continue to seek new markets or create new capabilities like global communication networks and high revisit-rate surface imaging, there is a need for constellations of satellites for these operations. To better manage the cost of deploying large quantities of satellites, companies working on LEO and cubesat designs prefer to use components that are not designed specifically for space deployment. However, commercial off-the-shelf (COTS) components often do not come with space heritage, space qualification, or even traceability or homogeneity of wafer lots, all of which are important requirements when the operating environment is unfriendly and unyielding.

The environment in space and its potential effect on components

The harsh environment means that COTS components cannot be used reliably for space missions without prior screening. There have been documented instances of engines failing to fire due to components not being space qualified. Electronic components must withstand significant shock and vibration during launch and separation, including pyrotechnic shock (the dynamic shock when an explosion occurs on a structure). It is critical that the integrity of the electrical connection is not compromised during the launch. This is true whether the satellite is being designed for deep or New Space.

The components often see wide temperature swings as satellites are heated by the sun then slip behind the Earth into very cold regions. During lunar day and night, the temperature of the moon can vary from around -200^oC to +200^oC. Most space parts must tolerate a vacuum, so transferring heat away from sensitive electronics is a challenge. Further, this environment encourages the creation of tin whiskers if pure tin, zinc and cadmium are used in the design. This can result in electrical shorts since they are electrically conductive.

Both cosmic and thermal radiation pose issues for space application designs, with the sun being the primary radiation source. There is no atmosphere to protect components from UV radiation, which can change the chemical structure of polymers and lead either to hardening or weakening of the material. This requires a careful choice of plating materials to reflect a broad spectrum of electromagnetic radiation. Parts must be clean and outgassing limited (reducing the vapor that comes off plastic devices causing contamination), to ensure, for example, that camera lenses are not clouded when in use; there is little tolerance for repairs in space.

Designing and building parts for space requires tenacity and a commitment to process, from managing electrostatic discharge, testing and training to handling analyses correctly and efficiently. 

Specification of space components

Procurement specifications for space are usually written for the requirement at hand. A scientific mission with a smaller budget will rely on the expertise of the manufacturer to assist in defining the technical details of the part and the required testing plan. A commercial satellite will have more detailed specifications, often defined at the satellite level rather than for the particular assembly required. Costs can mount as program managers sift through technical data and handle all contingencies.

All the above presents a challenge to understand what parts can and should be used. As with other high reliability applications, a certification is often necessary to make certain the environment is understood and characterized. The testing developed by the device manufacturer will ensure the components will operate as specified in a datasheet. As might be expected, these certifications are difficult to attain for several reasons:

• An understanding of the operating environment and how the tests must be set up to ensure proper test environments.
• An in-depth materials understanding so that the correct materials are utilized in the construction of the products under test.
• Experienced personnel to manage the work travelers and documentation to ensure each part is tested and specific information recorded according to the screening agreed.
• Sufficient equipment capability to enable the specific tests to be undertaken for the required number of parts: Ovens, bond pull, temp cycling, temperature shock, gross leak, HAST, vacuum bake, acceleration, vibration, shock, thermal analysis.

In order to develop systems effectively from a time and cost perspective, it is critical to be able to prototype the design within a relatively short period of time using COTS components, and subsequently, maintain the board design and components selection with the associated qualification screen completed. 

Who are the best fit as partners for space component development?

Companies that will be the best product development partners for space applications will have the following characteristics and skillsets:

• Will understand the space heritage, have many years or even decades of knowledge of what is required in such systems in order to build the quality processes into their standard commercial part design. Will have development and production process to ensure successful up-screening outcomes.
• Will understand and have the experience of running different test flows according to the application, platform, budget and requirements of the customer.
• Will have developed a robust product portfolio in die, hybrid and plastic or ceramic-based packages to support the complete signal chain needs of the satellite design.

It is very important for a partner to be familiar with the procedures and conditions of different level tests. As space modules will be developed in different packages and incorporate different components, there are a multitude of considerations for the testing:

• Die, hybrid, plastic or ceramic part to be tested. This will drive different MIL and NASA-level testing with their associated methods and conditions.
• Construction and robustness of designs. For example, is there adequate staking and fill in a module design to cope with the vibration effects of launch?
• Are optimum materials being used for plating and finishing to minimize critical issues, for example:
  1. Radiation
  2. Tin whiskering

Conclusion

The satellite industry is evolving as technology progresses. Many different platforms are now being developed based on needs of cost and size sensitivity and the considerations of the organizations developing them. This is spawning a whole array of platforms that have differing requirements in terms of form factors and related performance. One consistent requirement is the level of screening necessary to ensure the basic requirements of sustainable and trustworthy operation.

The companies best placed to succeed as partners to the space industry will be the ones who have deep experience developing robust products and who build quality into their design and manufacturing processes to ensure successful up screening outcomes. Companies that have experience addressing the needs of the various satellite payloads, data handling and control systems will be invaluable. With the proliferation of satellites being launched, schedules are being compressed, driving the need for COTS parts that are identical in construction to their high reliability siblings so that proof of concept can rapidly be followed by flight-ready parts.

About Marki Microwave

Marki Microwave has over 30 years of experience developing innovative products for space-qualified applications, having played an integral role in the success of several satellite programs. Select from standard products that support frequencies of up to 140GHz or contact us for custom products designed for your specific application. Marki has the capability to provide a space-qualified version of many of its COTS parts and supports Class K die qualifications, MIL-PRF-38535 for QML ceramic space grade products and PEM-INST-001 for plastic encapsulated microcircuits. To discuss part requirements and testing for your satellite design, please contact Marki Microwave.