Arianespace, Europe’s long-standing primary launch provider, flew the Sentinel-1D Earth observation satellite aboard the third Ariane 6 launch of 2025. The flight, only the fourth ever flown by the Ariane 6, successfully launched on Tuesday, Nov. 4, at 21:02 UTC from ELA-4 at the Centre Spatial Guyanais in Kourou, French Guiana.
All Ariane 6 flights to date have been the Ariane 62 variant with two Avio P120C solid rocket boosters, and Flight VA265 was no exception. The rocket took a northbound trajectory, placing the Sentinel-1D satellite in a Sun-synchronous orbit. The flight took just under 34 minutes to complete, from liftoff to a successful spacecraft separation.
This flight was the third commercial launch flown by the Ariane 6 family to date. The 54 m tall rocket, which used liquid hydrogen and liquid oxygen as propellants for its main stage’s Vulcain 2.1 and the upper stage’s restartable Vinci engine, used the 14 m tall “short” version of its payload fairing for this flight. A 20 m tall fairing is also available for payloads that need a larger volume.
The Vulcain 2.1 main engine ignited seven seconds before solid rocket booster ignition and liftoff. The two strap-on boosters separated at T+02:14 minutes after launch, and fairing separation occurred at T+03:28 minutes after liftoff. The Ariane 6 continued firing its core stage until T+07:43 minutes, when the upper stage separated.
The upper stage’s Vinci engine started eight seconds after stage separation, and Sentinel-1D separated from the stage at T+33:51 minutes after launch. The 2,184 kg Sentinel-1D, manufactured by Thales Alenia, was deployed to a circular Sun-synchronous orbit at an altitude of roughly 693 km.
After the Sentinel-1D satellite was released, the upper stage’s last activity will be to fire its engine for a deorbit burn at T+02:02:00 minutes after launch. This is done to ensure that the second stage will not become hazardous space debris. The main stage, fairing, and solid rocket boosters are also disposed of; although the Ariane 6 rocket is not currently reusable, Arianespace is researching reuse technology for the future.
Fueling operations of the Sentinel-1D satellite in Kourou. (Credit: Arianespace)
The Sentinel-1D satellite joined the Sentinel-1C satellite, launched by a Vega-C rocket on mission VV25 in December 2024, and the Sentinel-1A satellite, launched in 2014 — both of which are in orbit to observe Earth with their synthetic aperture radar (SAR) instruments. The Sentinel-1 series is one of six currently under the Sentinel family, with each series observing Earth with different methods.
Sentinel-2 is the counterpart to Sentinel-1 for optical Earth observation, while Sentinel-3 is designed for global ocean and land monitoring. Sentinel-4 missions are not performed by dedicated satellites, but instead use hyperspectral imaging instruments from satellites based in geosynchronous orbit. Sentinel-5P was a precursor mission to the Sentinel-5 series, to maintain data continuity for specific observations after the loss of the Envisat satellite in 2012.
Sentinel-5, like Sentinel-4, utilizes instruments based on those of other satellites for monitoring atmospheric composition, whereas Sentinel-6 missions employ dedicated satellites. Sentinel-6 satellites are designed to monitor sea levels with high precision and maintain data continuity from the Jason-3 mission, launched in 2016.
Radar image of the Danish coast taken by a Sentinel-1 series satellite. (Credit: Copernicus Programme)
The Sentinel family of satellites is operated by the European Space Agency (ESA) in support of the Copernicus Programme, which is managed by the European Union’s executive branch, the European Commission. The Copernicus Programme, an outgrowth of the European Union’s Global Monitoring for Environment and Security Earth observation system initiative, was formally established in 2014.
The Copernicus Programme, a component of the European Union Space Programme since 2021, gathers data from the Sentinel family of satellites as well as from satellites like the Landsat series and others operated by different space agencies on a contributing basis. This information is combined with in situ data from ground-based and airborne sources and distributed freely to all users and the public.
Data gathered by Earth observation satellites is used for studying the Earth’s oceans, atmosphere, forests, deserts, urban areas, ice caps, and for many other applications. Tracking glacial retreat, sea ice, oil spills, illegal logging in forests, illegal fishing, ground deformation, animal migration, and many other activities are just a few examples of how Earth observation data are used in the real world.
Ice flow in Greenland captured by the Sentinel-1 satellites. (Credit: Copernicus Programme)
The Sentinel-1D and its Sentinel-1C sister satellite are designed to observe Earth with a C-band SAR, manufactured by Airbus, that can be used at night and to “see” through adverse weather and cloud cover. Sentinel-1C was used to replace the failed Sentinel-1B satellite, which was part of a constellation of two satellites observing from the same orbital plane but 180 degrees apart. Meanwhile, Sentinel-1D will replace the aging Sentinel-1A satellite.
The Sentinel-1C and 1D satellites will maintain a six-day revisit cycle for continuous radar coverage of any given point on Earth. The Sun-synchronous orbit also ensures that the satellites view any given point on Earth at the same local time each day. Both satellites are equipped with an automatic identification system payload that receives signals from maritime vessels as well as Galileo-enabled receivers for precise positioning.
The Sentinel-1 series C-SAR instrument offers a spatial resolution of five meters and a 410 km swath. The data gathered is transmitted to the ground using a 520-megabit X-band link over two independent channels. In addition, the Sentinel-1 series offers four operational modes: strip-map mode, interferometric wide swath mode, extra wide swath mode, and wave mode.
Illustration of a Sentinel-1 series C-band radar observation satellite in orbit. (Credit: ESA/Mlabspace)
The strip-map mode offers an 80 km swath and a spatial resolution of five meters by five meters; it is used for emergency management and observing small islands. The interferometric wide swath mode offers a 250 km swath and five-meter by 20 m spatial resolution; it is the satellite’s main observation mode over land.
The extra-wide swath mode offers a 400 km swath and a 20 m by 40 m spatial resolution; it is used to monitor coastal areas for hazards and shipping. The wave mode offers a five-meter by five-meter resolution and produces 20 km by 20 km sample images at intervals of 100 km; it is the primary operational mode over the open ocean.
The Sentinel-1 series has a design life of over seven years, with 12 years of consumables. However, Sentinel-1B’s mission ended just over six years after its launch due to a power issue that disabled its radar instrument. During Sentinel-1D’s expected seven-year mission, newer members of the Sentinel family are expected to fly, numbered from Sentinel-7 to Sentinel-12.
The Ariane 62 launching the MetOp-SGA1 satellite and its Sentinel-5 atmospheric composition monitor on Aug. 12, 2025. (Credit: Arianespace)
These satellites will monitor anthropogenic (human-made) emissions, land surface temperature, ice and snow topography, hyperspectral imaging, microwave radiometry, and L-band SAR observations. The next satellite in the Sentinel family to fly is Sentinel-6B, scheduled to fly no earlier than Sunday, Nov. 16, atop a Falcon 9 from Vandenberg Space Force Base in California.
The next Ariane 6 flight, also an Ariane 62, is scheduled to fly two Galileo navigation satellites no earlier than December. The Ariane 64, with four solid rocket boosters, is expected to start flying in 2026, with its first flight being for the Amazon Kuiper broadband constellation.
(Lead image: Ariane 62 launches on mission VA265 with the Sentinel-1D satellite on Nov. 4, 2025. Credit: Arianespace)
The post Ariane 6 launches the Sentinel-1D Earth observation satellite appeared first on NASASpaceFlight.com.
Comments
Post a Comment