Oceans: Earth Observation satellites

Earth Observation can help us to better understand Ocean health and status, as well as keeping them clean of debris, provided we take action.

Multiple satellite missions are launched every year for all kind of industries (navigation, defense, exploration, among others), and an industry that is a must for keeping the Planet safe is Earth Observation (EO). Earth observation is a multimillion dollar industry. Recently (January 2024), the EUSPA (EU Agency for the Space Programme) released a market report on Earth Observation and GNSS, which together worth more than 260 thousand million euros.

Remote sensing is the technology for the monitoring of Earth and its resources via signals. Such signals can be translated into radiofrequency measurements, such as power, phase, doppler frequency, among others, whose purpose is to retrieve information on Earth surface through their interaction (reflections and/or refraction) with it. Not limited to RF measurements, signals can also be translated into images, for example microwave or optical images, both referring to different regions of the frequency spectrum.

This blog post is a brief review of some of the satellite missions dedicated to monitor the most precious resource we have, that one whose lack would make life impossible, and whose presence is, among other factors, a product of the miraculously precise location of the Earth in its “Goldilock region” around the Sun: the Ocean. However, it is needless to say that regarding debris monitoring, keeping the Oceans safe and clean is a task out of the scope of satellite missions, and closer to our field of action.

Aqua

  • Earth water cycle study including air-sea energy fluxes, ocean evaporation, soil moisture and cloud forming.
  • Agencies: JAXA (Japan), NASA (USA), INPE (Brazil).
    Oribit: LEO.
    Period: 98.8 minutes.
    Repeat cycle: 16 days.
    • NOTE: it is important to differentiate between these two concepts. The satellite period refers to the time it takes for a satellite to complete an orbit. The repeat cycle refers to the time it takes for the satellite to pass exactly over the same point projected in the ground.

SWOT

  • Its name stands for Sea Water and Ocean Topography and this mission studies the variations in water bodies over time, extending from sea to lakes and rivers.
  • Agencies: NASA (USA), CNES (France), UKSA (UK), CSA (Canada).
    Oribit: LEO.
    Period: 102.9 minutes.
    Repeat cycle: 21 days.

CYGNSS

  • Is a passive remote sensing system, which means that exploits signals originally designed for a different purpose (in this case navigation signals). GNSS signals reflect on the Earth surface (GNSS-R concept), and CYGNSS satellites collect those reflections. The mission main purpose is to estimate and predict wind speeds in tropical cyclones. It is worth noting that CYGNSS has also been used to estimate sea surface topography and altimetry.
  • Agencies: NASA & NOAA (USA)
    Orbit: LEO.
    Period: 95 minutes.

Copernicus Sentinel 1 B/C

  • Imaging satellite missions whose main purpose is the monitoring of sea and land ice, as well as marine speeds, land surface motion, and surveillance of oil spills.
  • Agencies: ESA (Europe).
    Oribit: LEO.
    Period: 98.6 minutes.
    Repeat cycle: 12 days.

Sentinel 6 Michael Freilich

  • Sea surface topography, as well as water vapor used in models for weather prediction. Sea surface height is of greate impotance since is correlated to sea surface temperature, helping to monitor climate change. It also counts with GNSS-RO instruments, which is the other passive GNSS-based remote sensing technology, whose purpose is to estimate, among others, atmospheric water vapor and ionospheric data.
  • Agencies: ESA & EUMETSAT (Europe), NASA & NOAA (USA)
    Orbit: LEO.
    Period: 112 minutes.
    Repeat cycle: 10 days.

Dedicating effort to monitor Earth and its resources is always beneficial. Water covers approximately 70% of Earth, from which almost 97% is found in the Oceans.

Monitoring Oceans is of great importance to better understand water status all around the world. Furthermore, it can help us keeping the Oceans clean when it comes to debris, although this task exceeds Earth Observation satellite missions, and is instead in our field of action.

Keep an eye on spacewayfinder.com: see this blog post which presents ongoing initiatives as well as how these EO missions are applied to detect Sea debris while doing of the Ocean a healthier place.

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