The European Space Agency’s seventh Earth Explorer mission, Biomass, launched on Tuesday aboard an Arianespace Vega-C rocket. Biomass, which will study Earth’s forests and their impact on the planet’s climate, lifted off from Kourou, French Guiana, at 09:15 UTC (6:15 AM local time).
The Earth Explorer missions are part of the Living Planet Programme (LPP), managed by the Earth Observation Programmes Directorate of the European Space Agency (ESA). These missions are dedicated to utilizing innovative technologies to help scientists gain a deeper understanding of our world. Selected in May 2013 from three candidate missions, Biomass will use synthetic aperture radar (SAR) to measure the biomass of forests with a particular focus on Earth’s tropical regions.
📺 Watch live: the launch of @ESA_EO's Biomass mission on Vega-C #VV26, liftoff scheduled for 29 April, 10.15 BST/11.15 CEST. #ESAwebTV coverage starts 09.55 BST/10.55 CEST. More details 👇https://t.co/u2Eb9ttKGT
— European Space Agency (@esa) April 25, 2025
While satellite-mounted SAR payloads are relatively common, ESA describes the instrument aboard Biomass as the first P-band radar to be used in space. This refers to the part of the electromagnetic spectrum in which it operates, with P-band being an alternative name for a portion of the ultra-high frequency (UHF) band. The instrument aboard Biomass operates at a frequency of 435 megahertz, resulting in a longer wavelength than SAR payloads in previous missions, which have utilized higher-frequency parts of the spectrum, such as the L and X bands.
SAR is an active-scanning sensing technology, where the satellite emits radio signals that are reflected back from Earth’s surface. Taking advantage of the satellite’s motion in orbit, clever processing techniques enable readings to be taken with a smaller antenna that would have required a much wider one if the satellite were stationary — hence the “synthetic aperture.”
Biomass after its arrival in Kourou. (Credit: ESA/CNES/Arianespace)
On the Biomass mission, a combination of polarimetry and interferometry will be performed using the SAR payload. These rely on measuring the change in polarization of the radar signal and the interference between multiple waves. These techniques allow for a detailed picture of the surface to be built up. The P-band radar aboard Biomass is key to its mission, giving it the ability to peer through layers of vegetation and build a detailed image over time of how forests are structured — allowing the satellite to literally see the wood from the trees.
This data will allow scientists to build a profile of the biomass in Earth’s forests, helping refine estimates of how much carbon they store. It will also aid in monitoring how forests are changing through processes such as deforestation and regrowth. Other applications include studying the topology of the forest floor, the structure of ice sheets, and the underlying structure of desert regions.
ESA selected Airbus Defence and Space as the prime contractor for Biomass, with construction taking place in the UK. Companies from twenty ESA member nations have been involved in the development of the satellite, with US and Canadian companies also contracted for components. The radar imaging payload was built by Airbus in Germany, with the American firm L3Harris constructing its deployable 12 m reflector antenna. The satellite has a mass of 1,131 kg and is expected to operate for at least five years in an orbit 666 km above Earth’s surface, inclined at 98 degrees.
Arianespace launched Biomass using its Vega-C rocket. Vega-C is a four-stage vehicle that first flew in 2022 as an upgraded successor to the original Vega, which completed 22 launches between February 2012 and September 2024. It is the smaller of the two rockets operated by Arianespace, complementing the much larger Ariane 6. Tuesday’s launch is designated VV26; it is the fourth flight of Vega-C and the 26th mission overall for the Vega family.
Vega-C VV26 on the launch pad during payload mating operations. (Credit: Arianespace)
All Vega-C rockets launch from the Zone de Lancement Vega (ZLV) at the Centre Spatial Guyanais (CSG) in Kourou, French Guiana. This was formerly Ensemble de Lancement Ariane 1 (ELA-1), used by the Ariane 1, Ariane 2, and Ariane 3 rockets between 1979 and 1989, before being rebuilt for Vega ahead of its 2012 debut. ELA-1 was itself built on the site of an earlier launch pad, which had been constructed for the unsuccessful Europa launcher project.
The launch campaign for Biomass and VV26 began on Feb. 28, when work to integrate the lower stages of the launch vehicle commenced. The satellite arrived in French Guiana on March 7 and was unpacked and loaded with propellant ahead of its mating with Vega’s Vampire payload adaptor. On April 14, Biomass was encapsulated in the payload fairing that will protect it during the ride into space. The upper composite, including the mated satellite, adaptor, and fairing, was transported to the launch pad three days later and installed atop the rocket on April 18.
Vega-C consists of three solid-fuelled stages with a liquid propellant fourth stage to complete orbital insertion. As Arianespace conducts its countdown in French, the moment of liftoff is referred to as “H0,” or “heure 0,” rather than T0. At this moment, the first stage P120C motor will ignite and propel VV26 skyward. This stage will power the ascent for approximately two and a half minutes, at which point the first stage will separate, and the second stage’s Zefiro-40 will take over, followed by the third stage, the Zefiro-9A. The payload fairing will separate early in the third stage burn.
Once the three solid-fueled stages completed their burns, the mission entered a brief coast phase as the combined third stage, fourth stage, and payload continued to climb towards the apogee — or highest point — of their trajectory. About seven minutes and 10 seconds after launch, the third stage separated, ahead of fourth stage ignition at the eight-minute mark in the flight.
The fourth stage is the Attitude and Vernier Upper Module+ (AVUM+), equipped with a restartable RD-843 engine. This stage completed three burns during the VV26 mission, with the second beginning about 53 minutes after liftoff, following another coast phase. Biomass separated from its payload adaptor shortly after the end of this burn, with AVUM+’s third burn occurring almost 50 minutes after spacecraft separation to ensure the safe disposal of the stage.
The Biomass launch follows Vega-C’s successful return to flight in December on the VV25 mission. This ended a two-year hiatus after the failure of its previous launch in December 2022. Vega-C is still in its qualification phase, with ESA overseeing the project. Arianespace’s next launch is expected to be another Vega-C, VV27, in July, which will deliver a four-satellite Earth imaging constellation to orbit for the French national space agency, CNES.
(Lead image: Vega C launches Biomass from Guiana Space Center – Credit: Arianespace)
