Small Satellites Step Forward

Artist's concept of one of the eight Cyclone Global Navigation Satellite System satellites deployed in space above a hurricane. Image courtesy of NASA.

Artist’s concept of one of the eight Cyclone Global Navigation Satellite System satellites deployed in space above a hurricane. Image courtesy of NASA.

We’re all about small satellites with this blog, after looking at the big beast that is GOES-R last week. Small satellites, microsatellites, cubesats or one of the other myriad of names they’re described as, have been in the news this month.

Before looking at what’s happening, we’re going to start with some definitions. Despite multiple terms being used interchangeably, they are different and are defined based around either their cubic size or their wet mass – ‘wet mass’ refers to the weight of the satellite including fuel, whereas dry mass is just the weight of satellite:

  • Small satellites (smallsats), also known as minisats, have a wet mass of between 100 and 500 kg.
  • Microsats generally have a wet mass of between 10 and 100 kg.
  • Nanosats have a wet mass of between 1 and 10 kg.
  • Cubesats are a class of nanosats that have a standard size. One Cubesat measures 10x10x10 cm, known as 1U, and has a wet mass of no more than 1.33 kg. However, it is possible to join multiple cubes together to form a larger single unit.
  • Picosats have a wet mass of between 0.1 and 1 kg
  • Femtosats have a wet mass of between 10 and 100 g

To give a comparison, GOES-R had a wet mass of 5 192 kg, a dry mass of 2 857 kg, and a size of 6.1 m x 5.6 m x 3.9 m.

Small satellites have made headlines for a number of reasons, and the first two came out of a NASA press briefing given by Michael Freilich, Director of NASA’s Earth science division on the 7th November. NASA is due to launch the Cyclone Global Navigation Satellite System (CYGNSS) on 12th December from Cape Canaveral. CYGNSS will be NASA’s first Earth Observation (EO) small satellite constellation. The mission will measure wind speeds over the oceans, which will be used to improve understanding, and forecasting, of hurricanes and storm surges.

The constellation will consist of eight small satellites in low Earth orbits, which will be focussed over the tropics rather than the whole planet. Successive satellites in the constellation will pass over the same area every twelve minutes, enabling an image of wind speed over the entire tropics every few hours.

Each satellite will carry a Delay Doppler Mapping Instrument (DDMI) which will receive signals from existing GPS satellites and the reflection of that same signal from the Earth. The scattered signal from the Earth will measure ocean roughness, from which wind speed can be derived. Each microsatellite will weigh around 29 kg and measure approximately 51 x 64 x 28 cm; on top of this will be solar panels with a span of 1.67 m.

The second interesting announcement as reported by Space News, was that NASA is planning to purchase EO data from other small satellite constellation providers, to assess the quality and usability of that data. They will be one-off purchases with no ongoing commitment, and will sit alongside data from existing NASA missions. However, it is difficult not to assume that a successful and cost effective trial could lead to ongoing purchases, which could replace future NASA missions.

It’s forecast that this initiative could be worth in the region of $25 million, and will surely interest the existing suppliers such as Planet or TerraBella; however, in the longer term it could also attract new players to the market.

Finally in non NASA small satellite news, there was joint announcement at the start of the month by the BRICS states (Brazil, Russia, India, China and South Africa) that they’d agreed to create a joint satellite constellation for EO. No further detail is available at this stage.

Once again, this shows what a vibrant, changing and evolving industry we work in!

GOES-R Goes Up!

Artist impression of the GOES-R satellite. Image courtesy of NASA.

Artist impression of the GOES-R satellite. Image courtesy of NASA.

On Saturday, 19th November, at 10.42pm GMT the Geostationary Operational Environmental Satellite-R Series (GOES-R) is due to be launched from Cape Canaveral in Florida, USA.

The GOES-R is a geostationary weather satellite operated by the National Oceanic & Atmospheric Administration (NOAA) Department of the US Government. It will the latest in the NOAA’s GOES series of satellites, and will take the moniker GOES-16 once it is in orbit, joining the operational GOES satellite constellation comprising of GOES-13, GOES-14 & GOES-15.

It will be put into a geostationary orbit at around 35 800 km above the Earth which will allow it to match the Earth’s rotation, meaning that it will effectively stay over a specific point on the Earth. It will be located approximately at 137 degrees West longitude, and through the constellation will provide coverage for North, Central and South America together with the majority of the Atlantic and Pacific Oceans.

Artists impression GOES-R satellite and its instruments. Image courtesy of NASA.

Artists impression GOES-R satellite and its instruments. Image courtesy of NASA.

The instrument suite aboard the satellite has three types: Earth facing instruments, sun facing instruments and space environment instruments.

Earth Facing Instruments: these are the ones we’re most excited about!

  • Advanced Baseline Imager (ABI) is the main instrument and is a passive imaging radiometer with 16 different spectral bands: two visible bands – Blue and Red with a spatial resolution of 0.5km, four near-infrared with spatial resolutions of 1 km; and ten infrared bands with a spatial resolution of 2 km. As its in a geostationary orbit its temporal resolution is extremely high with the full mode being where the Western Hemisphere is imaged every 5 – 15 minutes, whereas in its Mesocale mode (providing a 1000 km x 1000 km swath) the temporal resolution is only 30 seconds.
  • Geostationary Lightning Mapper (GLM) is, as the name suggests, an instrument that will measure total lightning, and both in-cloud and cloud-to-ground lightning across the Americas. It is an optical imager with a single spectral band of 777.4 nm which can detect the momentary changes in the optical scene caused by lightning. The instrument has a spatial resolution of approximately 10 km.

Sun Facing Instruments

  • Extreme Ultraviolet and X-ray Irradiance Sensors (EXIS) instrument has two sensors to monitor solar irradiance in the upper atmosphere; these are the Extreme Ultraviolet Sensor (EUVS) and the X-Ray Sensor (XRS).
  • Solar Ultraviolet Imager is a telescope monitoring the sun in the extreme ultraviolet wavelength range.

Space Environment Monitoring Instruments

  • Space Environment In-Situ Suite (SEISS) consists of four sensors:
    • Energetic Heavy Ion Sensor (EHIS) to measure the proton, electron, and alpha particle fluxes at geostationary orbit.
    • Magnetospheric Particle Sensor (MPS) is a magnetometer measuring the magnitude and direction of the Earth’s ambient magnetic field; and has two sensors the MPS-LO and MPS-HI.
    • Solar and Galactic Proton Sensor (SGPS) will, as the name indicates, measure the solar and galactic protons found in the Earth’s magnetosphere.
  • Magnetometer will measure of the space environment magnetic field that controls charged particle dynamics in the outer region of the magnetosphere.

The ABI instrument is the most interesting to us in terms of Earth observation, and it will produce a remarkable 25 individual products including Aerosol Detection, Cloud and Moisture Imagery, Cloud Optical Depth, Cloud Particle Size Distribution, Cloud Top Measurements, Derived Motion Winds & Stability Indices, Downward Shortwave Radiation at the Surface, Fire/Hot Spotting, Hurricane Intensity Estimation, Land Surface Temperature, Moisture & Vertical Temperature Profiles, Rainfall Rate, Reflected Shortwave Radiation at the Top Of Atmosphere, Sea Surface Temperature, Snow Cover, Total Precipitable Water and Volcanic Ash. If you want to look at the details of specific products then there are Algorithm Theoretical Basis Documents (ABTDs) available, which are like a detailed scientific paper, and can be found here.

The GOES-R is the first in a series of four satellites to provide NOAA with improved detection and observation of environmental events. It is not a cheap series of satellite, with the cost of developing, launching and operating this series estimated to be around $11 billion. However, this will provide observations up to 2036.

We’re excited by this launch, and are looking forward to being able to utilise some of this new generation weather information.