Introduction

Embarking on a new kind of adventure, scientists are using small satellites called CubeSats to explore the mysteries of water on Earth. They can help us learn more about oceans, lakes, and rivers. Water sustains all forms of life but, for something so integral to our existence, we know little about its intricate dynamics. This is where the collaboration between space technology and water research comes into play. CubeSats provide an approach for estimating river flows through remote sensing by enabling daily monitoring at sub-catchment scale, thus enhancing water management and research (Junqueira et al. 2021). For example, they are enabling the production of high-resolution, daily evaporation estimates for agricultural fields, enhancing water management and agricultural decision-making through revolutionary Earth observation capabilities (Aragon et al. 2021).

CubeSat Missions for Water Research

In an era where innovation knows no bounds, a project named Seahawk, a CubeSat mission developed by the University of North Carolina Wilmington (UNCW) in collaboration with National Aeronautics and Space Administration (NASA), Cloudland instruments, and AAC Clyde Space demonstrates the role of CubeSats in our aquatic ecosystems (Smith, 2021). 
"Our goal from the beginning was to integrate this mission into the infrastructure that we have built over the past 25 years to support ocean color satellites, and to demonstrate that a CubeSat can be treated like a normal, credible scientific mission. We had never dreamed this little satellite would still be operating after three years, let alone demonstrating new capabilities that we had never envisioned during development. And because they are smaller and less expensive, it will be easier to quickly adapt the second and third generations of CubeSats in a series to take advantage of what we have learned." - Gene Feldman, NASA ocean scientist (Smith, 2021)

The SeaHawk CubeSat is a compact 3U CubeSat, measuring 30 x 10 x 10 cm and weighing approximately 5 kg (Smith, 2021). This miniature satellite is designed to carry the HawkEye Ocean Color Imager and operates in low Earth orbit. The SeaHawk program represents a leap forward in the field of ocean color observation. By monitoring ocean color, it provides insights into marine ecosystems, climate processes, and coastal environments. 

Launched on December 3, 2018, the SeaHawk CubeSat is equipped with HawkEye instrument. It is a multispectral ocean color imager with an altitude of 540 km and 120 m resolution (Schueler and Holmes, 2016). The CubeSat's resolution is higher than that of other ocean color satellites such as Ocean and Land Colour Imager (OLCI) aboard Sentinel-2 which has a spatial resolution of 300 m and Visible Infrared Imaging Radiometer Suite (VIIRS) aboard NOAA-20 which has a spatial resolution of 375 m (WMO Oscar, 2023), therefore, enabling the observation of small-scale features and processes. Figure 1 portrays the high-resolution imagery that the CubeSat can produce.

By launching SeaHawk with 64 other satellites one after another, the program shows that smaller satellites can be a cheaper option. Regular satellites often cost a lot, making it hard to monitor water continuously. In this program, they used a constellation of smaller CubeSats, which cost less than bigger satellites and made it more affordable (Smith, 2021). 

The program stands as a success story in demonstrating the efficiency and value of CubeSat technology in advancing water research, particularly in ocean color observation. This initiative has demonstrated how CubeSats can revolutionize the field of water research by providing high-resolution, cost-effective, and continuous monitoring of Earth's aquatic environments. By deploying multiple CubeSats in coordinated constellations, a broader and more comprehensive coverage of Earth's aquatic environments can be achieved. This approach also reduces revisit times and enables more frequent data collection for timely and accurate monitoring. 

However, it is crucial to address certain limitations and consider areas for improvement. One challenge lies in achieving very high spatial resolution. The ability to provide extremely high-resolution imagery is essential for comprehensive water monitoring, especially in areas where small water bodies, often only a few meters wide play a significant ecological role. 

A similar study involving CubeSats called “Arctic-Boreal Lake Dynamics Revealed Using CubeSat Imagery” where scientists embarked on a mission to uncover the mysteries of thousands of small lakes in northern Canada and Alaska took place during the summer of 2017. Over 150 CubeSats formed a network, making daily observations of more than 85,000 lakes (Cooley et al. 2019). This mission captured fine-scale, short-term changes in the lakes' water levels revealing unexpected variability. It provided high-resolution images with approximately 3-meter resolution. However, the CubeSat data poses challenges. Location data from CubeSats is less precise than that from space agency satellites. Additionally, CubeSat images lack filters for easier analysis unlike NASA or European Space Agency (ESA) satellite data which are filtered to remove images taken on cloudy or low-quality days (Stacey, 2019).

The study used CubeSats' images captured by Planet Labs and unveiled that the observed lakes were far more dynamic than previously thought. Shorelines shifted, lakes expanded and contracted, and hundreds of square kilometers of lake area underwent transformation within a single season. The ancient Canadian Shield, a rugged terrain covering central Canada emerged as particularly dynamic (Stacey, 2019). 

With CubeSats, innovative algorithms and dedicated researchers, the monitoring of Arctic and sub-Arctic lakes could lead to crucial insights into preserving our planet's delicate ecosystems in the face of climate change. Figure 2 shows images captured by a private sector operator of CubeSats called Planet Labs. This CubeSat data played an important role in the research project led by Sarah Cooley that tracked rapid changes in lakes across diverse northern locations and offered valuable insights into the dynamics of water surfaces in the Arctic-Boreal regions of Alaska and Canada.

The SeaHawk mission equipped with the HawkEye Ocean Color Imager is designed to advance water research particularly in ocean color observation while Sarah Cooley's study using CubeSats aimed to investigate water dynamics in thousands of small lakes across northern Canada and Alaska. The study focused on the variability of water levels in these lakes during the summer using a network of CubeSats to capture fine-scale and short-term changes in water levels.

Challenges

There are challenges and concerns that need to be addressed. The large amount of data from CubeSats necessitates the development of sturdy data processing pipelines and effective algorithms that can unveil valuable insights. Moreover, ensuring the security and privacy is of importance in scenarios where sensitive areas are under observation. Additionally, as CubeSat deployment increases, the concern of space debris becomes more prominent which highlights the significance of addressing proper end-of-life disposal methods to ensure long-term space sustainability.

Conclusion

CubeSats are revolutionizing water research. Their cost-effectiveness makes it possible to monitor water continuously. While CubeSats offer many advantages, there are challenges, such as handling a large amount of data, ensuring security, and dealing with space debris. 

Looking ahead, CubeSats with special sensors can play a crucial role in disaster response, pollution detection, studying surface water dynamics and education. CubeSats with specialized sensors can be used in watersheds and reservoirs to keep an eye on water quality, temperature, and pollution. This information helps water managers make smart choices about treating and distributing water and ensuring that it is safe for communities. In times of natural disasters like hurricanes or floods, CubeSats can facilitate damage assessment and help to keep an eye on possible environmental problems. The data allows disaster response teams to coordinate help and figure out where to focus resources. CubeSats can also help spot oil spills and pollution in water bodies early on.

Using CubeSat data and pictures in education can inspire the next group of scientists, engineers, and people who care about the environment. Students can learn about how CubeSats are used in real life to study water, combining space exploration and taking care of our environment. To learn more about CubeSats we recommend the KiboCube academy.