The Small and Mighty Proba Missions

This week the European Space Agency announced the latest mission in the Project for OnBoard Automony (PROBA) mini-satellite programme. Proba-3 is planned to launch in four years; and will be a pair of satellites flying in close formation, 150m apart, with the front satellite creating an artificial eclipse of the sun allowing its companion views of the solar corona; normally only visible momentarily during solar eclipses.

Tamar estuary captured in October 2005, data courtesy of ESA.

Tamar estuary captured in October 2005, data courtesy of ESA.

The Proba missions are part of ESA’s In-orbit Technology Demonstration Programme, which focuses on testing, and using, innovative technologies in space. Despite Proba-3’s nomenclature, it will be the fourth mission in the Proba programme. The first, Proba-1, was launched on the 22nd October 2001 on a planned two year Earth observation (EO) mission; however despite the planned lifecycle, thirteen years later it is still flying and sending back EO data. It’s in a sun synchronous orbit with a seven-day repeat cycle and carries eight instruments. The main one is the Compact High Resolution Imaging Spectrometer (CHRIS), developed in the UK by the Space Group of Sira Technology Ltd that was later acquired by Surrey Satellite Technology Limited. CHRIS is a hyperspectral sensor that acquires a set of up to five images of a target, with different modes allowing the collection of up to 62 spectral wavebands.

Plymouth, where Pixalytics is based, and our lead consultant, Dr Samantha Lavender, have a long history with Proba-1. Rame Head point, along the coast from Plymouth, is one of the test sites for the CHRIS instrument and she’s been doing research using the data it provides for over a decade. Over Plymouth Mode 2 is used, which focuses on mapping the water at a spatial resolution of 17m; this mode was proposed by Sam back in the early days of CHRIS-Proba. The image at the top of the page, captured in October 2005, shows the Tamar estuary in the UK that separates the counties of Devon and Cornwall; for this image CHRIS was pointed further North due to planned fieldwork activities. At the bottom of the image is the thick line of the Tamar Road Bridge and below it, the thinner Brunel railway bridge. Plymouth is to the right of the bridge, and to the left is the Cornish town of Saltash.

Proba-V image of the Nile Delta in Egypt, courtesy of the Belgian PROBA-V / ESA Earth Watch programmes

Proba-V image of the Nile Delta in Egypt, courtesy of the Belgian PROBA-V / ESA Earth Watch programmes

Proba-2 was launched in 2009, carrying two solar observation experiments, two space weather experiments and seventeen other technology demonstrations. ESA returned to EO for the third mission, Proba-V, launched on the 7 May 2013; the change in nomenclature is because the V stands for vegetation sensor. It is a redesign of the ‘Vegetation’ imaging instrument carried on the French Spot satellites; it has a 350m ground resolution with a 2250km swath, and collects data in the blue, red, near-infrared and mid-infrared wavebands. It provides worldwide coverage every two days, and through its four spectral bands it can distinguish between different types of land cover. The image on the right is from Proba-V, showing the Nile delta on 2nd May 2014.

Despite their small stature all the Proba satellites are showing their resilience by remaining operational, and they’re playing a vital role in allowing innovative new technologies to be tested in space.