High contact density connectors in nanosatellite network

As a result, a large proportion of the Earth’s population still does not have the benefits of the next generation voice/data services that are already commonplace elsewhere.

To give some idea of the extent of the problem, it is estimated that currently around three billion people remain unable to gain access the Internet (according to research undertaken by the World Economic Forum). These are generally located in areas of Africa and South America, as well as remote regions of Asia. Such circumstances have severe impact upon them; in relation to their economic welfare, health and education too.

Australian communications provider Sky and Space Global is looking to change all this. Rather than relying on conventional terrestrial networks, it plans to offer services through the implementation of its latest nanosatellite constellation. Referred to as ‘The Pearls’, this will comprise about 200 nanosatellites, located in low Earth orbit (LEO) above the Earth’s surface – in orbital rings near the equator. 

The objective of this arrangement is to provide more cost-effective and affordable communication capabilities to parts of the world where it has so far been impractical to do so and are therefore acutely underserved. 

The multitude of nanosatellites that makes up ‘The Pearls’ constellation are all fitted with a three metre expanse of sun-tracking photovoltaic panels, through which solar energy can be acquired. Each one will be positioned into orbit evenly spaced from other nanosatellites creating an orbital ‘necklace’. With communications frequencies residing in the S band (two to four gigahertz). At the same time they will also have the capacity to communicate with one another, hence each satellite is acting as a router.

It will take each of the nanosatellites approximately 90 minutes to circle the globe. As they continue through their orbit, they will hand over communication coverage of the area they had been looking after to the next nanosatellite in the chain (and subsequently take on the coverage responsibilities from the preceding nanosatellite). This process will keep on being repeated. By forming an unbroken ring of nanosatellites in this way, the narrowband wireless coverage will be maintained at all times. 

Via this ambitious venture, it will be possible for voice, messaging, IoT and M2M communication services to be made available without heavy costs. It follows on from the success of the company’s ‘Three Diamonds’ constellation, which was launched into space back in mid 2017. 

Consisting of just three nanosatellites, this mission was established to test the feasibility of all the building blocks of the larger scale project, validating that both the coverage delivery and the hand over functions could be accomplished effectively. 

Danish satellite specialist GomSpace, which had already been involved in the test project, won an international bid to develop the nanosatellites required for ‘The Pearls’ constellation. Since then its engineers have been working closely with the UK branch of SAS on defining the exact requirements of the hardware design and the key attributes of all the constituent components. 

In order to minimise both the launch payload and ongoing power consumption, each of these nanosatellites will have a diminutive form factor, with external dimensions of no more than 24x45x12cm. This means that all the essential electronic circuitry must be squeezed into an extremely confined space. 

It has been critical, from both an economical and a logistical perspective, that the nanosatellite design should, as much as possible, feature commercial off-the-shelf (COTS) components rather than rely on the use of custom designed products. Sticking to this tactic has not only helped to avoid accruing hefty upfront costs and kept the overall budget in check, but also resulted in ease of manufacture and significantly shortened the development time.

With the project already underway, Harwin first began to engage directly with GomSpace a little over a year ago, with the companies’ respective engineering teams entering into in-depth discussions on how best to go about dealing with all the connectivity considerations. Based on their compact size, lightweight plastic-shelled construction and innate ruggedness, various members of Harwin’s Gecko latched connector series would be specified. 

These high contact density, narrow pitch (1.25mm) connectors have been employed in a host of space-related projects in recent years. Possessing industry-leading resistance to shock and vibration, as well as having an operational temperature range that spans from -65 to +150°C, they present an ultra-high reliability interconnect solution. 

Another key advantage of the Gecko product series is its outgassing properties. These connectors perform far better than other connector offerings when placed into a vacuum (thereby safeguarding against a potential cause of faults in electronic circuitry). An initial quantity of 100 units was supplied for development. This was made up of both through-hole and surface mount versions (in six-pin to 34-pin formats), with more than 35 mated pairs being incorporated into every single nanosatellite. More units will be needed to complete the project and to meet ongoing requirements as individual nanosatellites are replaced over the course of the next decade. 

Klaus Ahlbech, Research & Development Director at GomSpace, explained: “For each nanosatellite we have numerous heavily populated boards that must be stacked closely together, with little headroom between them. Given that there is such limited space to play with, it is of paramount importance that we can utilise compact, low-profile components that contribute very little to the overall weight of the system. 

“These need to simultaneously exhibit high degrees of operational robustness to deal with the uncompromising nature of the application and also come at an acceptable price point, so that budgetary problems are not encountered. Harwin’s Gecko connectors have shown that they have all the characteristics mandated by this project, providing us with assured long term inter-board connectivity even in these challenging circumstances.

“As well as the continued technical advice that Harwin have provided, the company’s support when it came to tooling was of another important aspect. This enabled us to make much quicker progress through the early stages of hardware development and keep the project on schedule.” 

Production of the satellites is now underway and space deployment is due to commence in 2019. The nanosatellites will be in place and the constellation operational within the 2020 timeframe.