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!

Vienna!

Last week I was in Vienna, Austria, attending the 2014 European Geophysical Union (EGU) General Assembly. It was a scientific smorgasbord laid in front of over 12,000 people from 106 countries. Over 4,800 oral presentations were given and 9,500 posters displayed, this was coupled with a variety of other sessions and an exhibition; which created a varied programme. I really liked the plan to create smart umbrellas to collect rain data, which has already received press coverage.

My EGU experience began with a poster summary session on the Thursday morning; these are short three minute presentations giving delegates a flavour of the posters being displayed to encourage people to come and see them. I then moved onto watching presentations and visiting the posters.

Two presentations really caught my eye. The first was about NASA’s upcoming mission Cyclone Global Navigation Satellite System (CYGNSS) which will be studying ocean surface winds using reflected Global Navigation Satellite System (GNSS) signals that are primarily used for positioning, such as within your mobile phone, and timing measurements. This technique, often called GNSS reflectometry, was previously demonstrated on the SSTL’s UK-DMC-1 mission.

The second one focussed on using the altimeter SARAL/AltiKa to study storm Xaver that impacted the southern North Sea / northern Europe with hurricane force winds and a tidal surge at the beginning of December 2013. Launched in February 2013, SARAL/AltiKa is a new collaboration between the French Space Agency (CNES) and Indian Space Research Organization (ISRO) filling a gap left by the loss of ESA’s Envisat as it has the same ground track; while we wait for the Copernicus Sentinel-3 mission that will include altimetry, ocean colour and sea surface temperature instruments.

On the Friday I presented a poster on an ESA project I’m involved with titled E-Collaboration for Earth Observation (E-CEO), which addresses the technologies and architectures needed to provide a collaborative research platform for automating data mining and information extraction experiments. Our aim is to run Earth Observation challenges akin to those used to solve computing tasks, and the poster presented the first of the challenges – focusing on the atmospheric correction of ocean colour imagery.