Smallsat Technology for Low-Earth-Orbit Applications

Chapter 1

Satellite History (timeline)

A satellite is known as an object that orbits around a bigger object in space. There are two types of satellites you should be aware of: natural (e.g. the moon) or artificial (e.g. the International Space Station) [source].

You may or may not know that right now there are thousands of artificial satellites orbiting the Earth. There are more than 20 satellites alone that make up the Global Positioning System (also known as GPS), which helps you determine your location on your cell phone or in your car every single day. [source]

Satellites have a variety of roles and come in all shapes and sizes:

• Weather satellites - Meteorologists rely on these to help predict the weather. These satellites usually contain cameras that can relay photos of Earth’s climate from either a fixed point or from polar orbits. 
• Communications satellites - These allow data and telephone conversations to be relayed through the satellite. Two well-known communications satellites include Telstar and Intelsat.
• Scientific satellites - The Hubble Space Telescope is an example of a scientific satellite that performs various scientific missions. 
• Rescue satellites - These are known for helping respond to radio distress signals.
• Navigational satellites - The most famous satellites are the GPS Navstar satellites like we discussed briefly above. They help ships and planes navigate.
• Broadcast satellites - These broadcast TV signals from various points, just like communications satellites.
• Earth observation satellites  - We utilize these types of satellites to observe the planet for changes in anything from temperature to ice-sheet coverage, and anything in-between. 

Resource: https://science.howstuffworks.com/satellite1.htm

...So why are satellites so important? 

Satellites can see into space better than any telescope on Earth and thanks to their birds-eye-view, help scientists see more significant areas of Earth at one time. This means satellites can collect data quicker than other instruments that are on the ground. 

Over the years, TT Electronics has had a strong pedigree in supplying space missions with a variety of custom solutions dating back to 1977. You can see a variety of these below.

Notable TT Electronics Missions:

As technology has advanced throughout the years, the miniaturisation of computers, hardware and components soon followed. It’s now possible to send much smaller satellites into space that can perform the same functions in orbit as their former bigger counterparts.

In today’s space market, higher volume satellite constellations in low-earth orbit are becoming increasingly popular for enabling improved and more localised earth observation, surveillance and communication.

While deep space exploration often demands component survivability for 20 years or more in the harshest of environments, higher volume satellite constellations in low-earth orbit are driving a different requirement - cost-effective components destined for operational use for just three to five years in more benign conditions.

Now it’s common to send up smaller, cube-shaped satellites (also known as “CubeSats”) to operate in low-earth orbit.

The original goal of the CubeSat project, which started in 1999, was to give affordable access to space for university researchers, according to Alen Space.  Since then, the program has expanded to include:

• Scientific and educational institutions
• Public initiatives
• Private enterprise

...So what are small satellites exactly?

 A small satellite, also known as a “miniaturized satellite” or “smallsat” is a satellite of small size and mass, generally under 500 kg. [source] 

[Source: YouTube, Real World: CubeSats - A Satellite Small Enough to Fit in Your Hand, NASAeClips]

While all of these types of satellites technically can be called “small,” there are different ways to classify them based on their mass.

• Minisatellite: 100-500 kg
• Microsatellite: 10-100 kg
• Nanosatellite: 1-10 kg
• Picosatellite: ~1 kg

As we discussed before, these types of satellites conduct operations whilst positioned in a low-earth orbit. 

So what exactly is low-earth orbit and what demands come with these small satellites in the New Space market?

Keep reading on to find out in the next chapter.

Chapter 2

Demands and Responsibilities of Low-Earth Orbit (LEO) Satellite Applications

Within the last two decades, since the CubeSat fundamentally advanced the satellite industry, the space market has boomed significantly as a result of commercialisation in space and an increasing demand for low-earth orbit satellite applications .

LEO satellites operate from 200 km to 2,000 km above the Earth’s surface. Traditional communication satellites are stationed much higher in a geostationary orbit up at around 36,000 km.

Source: https://www.sciencedirect.com/topics/engineering/low-earth-orbit

These satellites are much smaller than conventional satellites, and the new mindset has shifted to focus on cost, capability, and scale.

“It’s a different mindset... You need to get it up there quickly. It needs to meet the basic requirement, and you need to be able to replenish the constellation,” said Marina Mississian, Honeywell Aerospace Space Payloads senior director.

Despite their smaller size, these more compact satellites perform many of the same tasks as conventional satellites. 

This makes them suitable for many different industrial applications such as the following:

Communication

Small satellites have helped bridge the gap on a global scale by connecting areas of the world without land communication. There’s a “growing number of sensorised objects and networks requiring global connections and communications” [source].

Earth Observation

Like conventional satellites, these low-earth orbiting satellites are used to collect and interpret various data points to manage and improve the human population’s living conditions correctly. They can analyse human impact on agriculture, forestation, geology, and the environment, natural resources and more to develop sustainable economies across the globe.

Geolocation & Logistics

Locating and managing assets like aircraft, vehicles, ships, etc. in areas with no land cover can prove difficult and very costly; however, satellites in low-earth orbit can provide immediate monitoring anywhere on the planet.

Signal Monitoring

Radio signals transmitted from Earth can be monitored easily, which means in the event of a disaster, they can provide immediate information detailing the degree of impact and severely impacted areas, which in turn allow for more efficient rescue operations and relief work. 

Scientific Missions

Small satellites in low-earth orbit can be used for various science-related purposes like space observation, systems testing and research. Since they are more cost-effective than traditional satellites, they allow for the development of space programs in countries that have not joined the space race yet or for universities, companies or scientists to get their foot in the door in the exciting and rapidly expanding New Space market. 

What are the Advantages of Low-Earth Orbit for Satellites?

Since the satellites are closer to the Earth, that means the trip to and from the satellite is inevitably shorter-- a shorter trip is a less expensive trip. This means the latency (the time needed for data to be sent and returned) is far reduced for LEO satellites compared to those that are farther out. [source] The smaller size and weight requirements for these applications generally provide cost savings as well.

Not to mention, since signals travel faster through space compared to fibre-optic cables, LEO satellites can rival or even beat the fastest ground-based networks on Earth. 

The major downside of a low-earth orbit satellite is that the speed that’s needed for a stable orbit is reduced with distance. 

According to Greg Ritchie and Thomas Seal at Bloomberg, LEO satellites must travel at about 27,000 kph, completing a full circuit of the planet in 90 to 120 minutes. This means that an individual satellite is only in direct contact with a ground transmitter for a short period, and is one of the major reasons why LEO projects involve such a high volume of satellites. 

Responsibilities of the Satellite in Low-Earth Orbit  

Satellites must be able to communicate efficiently with Earth-based stations. Low-earth orbit is used for many communication applications.

Low-earth orbits are commonly used for remote sensing, human space flight, and data communication.[source: Aerospace Security, “Popular orbits 101,” Center for Strategic and International Studies, November 30, 2017]

Lower orbits can support remote sensing satellites. 

“Remote sensing generally refers to the use of satellite or aircraft-based sensor technologies to detect and classify objects on Earth. It includes the surface and the atmosphere and oceans, based on propagated signals (e.g. electromagnetic radiation).”

Most of the human-made objects orbiting Earth are in LEO.

Low-earth orbit satellites have higher orbital velocities, shorter orbital periods, and lower altitude above the Earth’s surface. [source: Low-earth orbit and Geostationary Satellites]

LEO satellites orbit between 200 and 2,000 kilometres above the earth.

For reference, the International Space Station orbits 400 km above the Earth’s surface.

Chapter 3 

Decommissioning of Satellites (Debris) Safely to Prevent Collisions

A safe and stable space environment is critical to the economy and national security systems. We depend on space technologies for communications, collecting weather data, and a variety of other critical purposes that affect almost all of us everyday. Satellites moving close to the Earth’s surface are ideal for making observations and additionally for a range of military supporting purposes.

However, there is a growing number of satellites in orbit that could potentially challenge that safety. The low-earth orbit environment is becoming increasingly crowded with space debris. Space debris is also known as space junk and orbital debris. The debris presents a growing threat to space operations. 

“Orbital debris, or space debris, means any human-made space object orbiting Earth that no longer serves any useful purpose”. [source] 

When a satellite completes its mission, and there is no more use for it, the satellite is decommissioned. Meaning its instruments are deactivated, and it moves into its final orbit for disposal. If a decommissioned satellite is not adequately handled or its constituent parts are no longer operational to activate the required movement for deorbiting, it could crash into other satellites causing damage. These collisions then commonly produce more space debris, in a domino-like effect known in the space community as the Kessler Syndrome.

The volume of debris collecting in low-earth orbit presents a real hazard: smaller debris is hard to track and can become very dangerous if coming into contact with unknown objects in space. These debris elements are extremely hazardous to working satellites.

FCC chairman Ajit Pai cites, 

“A collision between two satellites could have a catastrophic impact on the space environment for centuries to come.”

International guidelines recommend that operators remove satellites from low-earth orbit, which is roughly 1,200 miles above the earth’s surface, within 25 years from the end of the satellite’s mission. [source]

Improving our knowledge of the space environment and diminishing the effect of orbital debris is critical. The right sensors could help reveal space debris and educate mission planners further. 

As part of mission licensing, the space agencies that sanction launches must know the components operational lifetime - ensuring appropriate deorbiting and decommissioning of satellites to ensure no space debris is left in the atmosphere. This is where TT Electronics' New Space Electronics® play a cruical role, as our solutions deliver cost-effective performance using a fully traceable and space-proven die.

Today, modern technology is more adept in keeping up with the demand and better at communicating and monitoring space activity than older tracking systems. Satellites and their manufacturing methods are becoming more advanced.

Deloitte Insights states:

“Different commercial and government organisations are currently looking at changing the rules governing how conjunctions are handled, as well as how to deorbit satellites at their end of life safely. They are also exploring using machine learning algorithms and improving tracking technologies, such as ground-based radar, for managing the problem.

Chapter 4 

What are COTS (Commercial-Off-the-Shelf) Components and What You Need to Know

There’s currently a growing trend to use commercial-off-the-shelf components (COTS) in the space industry.

COTS are defined by NASA as, 

“An assembly or part designed for commercial applications for which the item manufacturer or vendor solely establishes and controls the specifications for performance, configuration, and reliability (including design, materials, processes, and testing) without additional requirements imposed by users and external organisations,” [source: The NESC 2014 Technical Update, NASA]

Why is there an increase in demand for these components?

Simply put, design engineers are considering opting to use these commercial components over a custom solution largely due to cost saving benefits that these commercial solutions provide. 

Should you rely on COTS components as a suitable industry solution for your high-reliability space application? 

It’s crucial to weigh the advantages and disadvantages of COTS to make this decision. 

According to Micro-Rel, the usage of COTS components in high-reliability space applications may offer you benefits such as:

1. A potential cost saving advantage - this only applies for large volumes or low reliability/low radiation application where significant risks might be taken.
2. Shorter lead times and lower risk of part unavailability - it’s essential to keep in mind the quick obsolescence cycle of COTS components due to their limited shelf life.

Despite the above benefits, it’s important to note that since these components are relatively new to the space market, proper methodologies are still in the process of being developed to allow a more systematic usage of COTS components for space applications.

The main disadvantages of COTS to be aware of include: 

1. Reliability - no traceability, quality inspections, or temperature range.
2. The mounting process can result in finish problems (e.g. tin whiskers).
3. Effects due to radiation - COTS often need radiation behaviour assessment, which can result in a long, costly and uncertain process.
4. Cost comparison - additional screening costs (such as radiation assurance) may be required to meet mission requirements before the parts can be used in low-risk space applications.

Source: [“COTS Components in Space Systems: Benefits and Risks,” Micro-Rel]
 

When deciding between COTS components versus a custom solution, it’s clear there is still a lot of uncertainty.

COTS solutions are less expensive but unproven with no guaranteed performance, while fully custom solutions can be expensive and result in long lead times.

If you're looking for a solution that's an in-between that provides assurances of performance whilst not incurring a significant custom-led pricing, our New Space Electronics® product range can offer you cost-effective screening but fully traceable and proven space-grade heritage.