Vega rocket readied for launch of Sentinel-2A Earth observation satellite
An Arianespace Vega launch vehicle is slated to send the European Space Agency’s (ESA) Sentinel-2A Earth-observing satellite aloft at 9:52 p.m. EDT on June 22 (01:52 GMT on 23 June) from ESA’s spaceport located in Kourou, French Guiana. The preparations for the flight, which was previously scheduled to take place on June 12, are in full swing as the spacecraft having been fueled, mated with the launch adapter, and encapsulated in the rocket’s payload fairing. The upcoming mission, designated Flight VV05, will be the fifth launch of the lightweight Vega rocket.
Built by Airbus Defence and Space, the 2,513 lbs. (1,140 kg) satellite will deliver high-resolution and multispectral imaging capabilities from its orbital perch. This should provide an 180 mile-wide (290 km) coverage path of the terrain below. The spacecraft will join the Sentinel-1A satellite that was placed into orbit on April 3, 2014, by a Soyuz-STA/Fregat rocket operating from the same ESA spaceport. Sentinel-2A will be put into a polar, Sun-synchronous orbit at an altitude of some 477 miles (786 km).
The spacecraft is equipped with the Multispectral imager (MSI) instrument which is capable of covering 13 spectral bands (443 nm–2190 nm). The instrument is touted as being the most advanced of its kind. In fact, it is the first optical Earth observation mission of its kind to include three bands in the ‘red edge’, which provide key information on the condition of vegetation far below.
The MSI works passively, by collecting sunlight reflected from the Earth. New data is acquired at the instrument as the satellite moves along its orbital path. The incoming light rays are split by a filter and focused onto two separate focal plane assemblies within the instrument: one for Visible and Near-Infrared (VNIR) bands and one for Short Wave Infrared (SWIR) bands. The spectral separation of each band into individual wavelengths is accomplished by stripe filters mounted on top of the detectors.
Sentinel-2A is planned to be operational for more than seven years. Sentinel-2A is the first part of a two-part constellation (Sentinel-2A and 2B). Once 2A is on orbit, the Earth’s land surface will be covered once every 10 days. When 2B is sent aloft, the pace will accelerate to once every 5 days.
After the arrival at the launch site at the end of April, Sentinel-2A has been put through a series of stringent tests to confirm there was no damage during the flight from Germany.
These tests were conducted to ensure that everything is in good working order so that this new satellite will deliver the images to monitor the status of Earth’s vegetation and its changing landscape.
The fueling of the satellite took place last week, after which it was integrated to the Vega adapter.
The protective covers were then removed before it was encapsulated in the rocket fairing. In the coming days, the satellite will be transferred the launch pad.
Vega is a single-body launcher with three solid-propellant stages and a liquid-propellant upper module for attitude and orbit control, and satellite release. With a height of 98 ft. (30 m) and a diameter of 9.8 ft. (3 m), the launcher is described as being capable of placing 660-3,300 lbs. (300–1500 kg) satellites into polar and low-Earth orbits used for many scientific and Earth observation missions.
The Sentinel-2 mission is dedicated to Europe’s Copernicus environmental monitoring program, which is headed by the European Commission in partnership with ESA.
If everything goes according to plan, the new satellite will provide information for agriculture and forestry, and also for helping to manage food security. The images will be used to determine various plant features such as leaf chlorophyll amount and water content.
As well as monitoring plant growth, the satellite will be used to map changes in land cover and to monitor the world’s forests. It will also provide information on the amount of pollution in lakes and coastal waters. Images of floods, volcanic eruptions, and landslides will contribute to disaster mapping and helping humanitarian relief efforts.
More specifically, the mission will monitor variability in land surface conditions, and its wide swath width and high revisit time (10 days at the equator with one satellite, and 5 days with 2 satellites under cloud-free conditions which results in 2-3 days at mid-latitudes) will support the monitoring of changes to vegetation within the growing season. The coverage limits are from between latitudes 56° south and 84° north.
Once Sentinel data is acquired on board, it will be sent to the ground and received at the X-band core stations located in Matera, Italy, Maspalomas, Spain, and Svalbard, Norway.
Data can also be transmitted via laser link to the European Data Relay System, which relays data via geostationary satellites to the ground where they are received at the user Ka-band stations.
Each Sentinel satellite has a high level of autonomy so that they can operate without any intervention from the ground for periods of up to 15 days.
The Sentinel mission has been designed and built by a consortium of around 60 companies led by Airbus Defence and Space, and supported by the CNES French Space Agency to optimize image quality and by the DLR German Aerospace Centre to improve data recovery using optical communications.
This flight will be Arianespace’s 5th mission this year, following two previous flights of Ariane 5 rockets, one Soyuz, and one Vega. The next planned Sentinel launch is currently slated to take place in the second half of 2016.
Video courtesy of the European Space Agency
Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration.