ADM-Aeolus: ESA's wind mission

Due for launch at the end of 2013, ADM-Aeolus (or just 'Aeolus'), is the fourth Earth Explorer mission to be developed within ESA's Living Planet Programme. Aeolus will be the first-ever satellite to directly observe wind profiles from space. 

Named after Aeolus, who in Greek mythology was appointed 'keeper of the winds' by the Gods, this mission will provide much-needed data to improve the quality of weather forecasts as well as contribute to long-term climate research.

The mission

Although weather forecasting has advanced considerably in recent years, meteorologists still need reliable wind-profile data to further improve the accuracy of forecasts. ESA's wind mission, ADM-Aeolus, aims to demonstrate that measuring global wind profiles from space, using laser technology, can meet this requirement.

The Aeolus Flight Operations Control Centre (FOCC) is being established at ESOC, Darmstadt, Germany.

The Flight Control Team

Piere Bargellini

The Aeolus Flight Control Team will operate from a Dedicated Control Room located at ESOC.

Spacecraft Operations Manager (SOM) Pier Bargellini, supported by Kate Adamson (Deputy SOM), will manage a team of spacecraft operations engineers dedicated to Aeolus. The team will be responsible for command and control, on-board software maintenance and mission planning, as well as interfacing with other ground segment teams. As with all satellites operated from ESOC, specialists from other support teams including Flight Dynamics, Ground Facilities and Software Support will contribute to the mission on a daily basis.

The Aeolus Flight Operations Segment development is progressing on schedule with several major milestones achieved successfully. Definition of the flight control procedures and assembly of the Flight Control Team are also being completed. Initial System Validation Tests between the Flight Operations Control Centre and the spacecraft have been conducted successfully. Training for the Flight Control Team will begin in earnest about 12 months prior to launch.

Mission operations overview

Dnepr vehicle during launch

The main aim of the mission is to further our knowledge of the Earth's atmosphere and weather systems.

By recording and monitoring the weather in different parts of the world, ADM-Aeolus will allow scientists to build complex models of our environment, which can then be used to help predict how that environment will behave in the future. ADM-Aeolus is expected to launch on a small-capacity booster; Aeolus is compatible with many small launchers, such as Vega, Rockot and Dnepr.

The Aeolus satellite will carry one large instrument, the Atmospheric Laser Doppler Instrument (ALADIN), which will probe the lowermost 30 km of the atmosphere from 400 km above the Earth's surface. The satellite will create a series of consistent global wind profiles for the first time (about 120 per hour), giving meteorologists better information with which to predict weather. From orbit, ADM-Aeolus will be able to provide wind profiles for the entire planet, including remote areas lacking ground-based weather stations.

Baseline Aeolus measurement geometry

ADM-Aeolus will fly in a rather low Sun-synchronous orbit at about 400 km altitude in a dusk-dawn orbit. The wind will be measured orthogonal to the flight direction at an angle of 35 degrees off-nadir on the night side of the Earth. An important factor in the satellite design is the need to minimise drag at the altitude chosen in order to minimise fuel consumption for orbit maintenance.

The concept for control of the Aeolus mission is based on the use of a single ground control centre in conjunction with ESA's ESTRACK ground station in Kiruna. The Launch and Early Orbit Phase (LEOP), as well as the Commissioning Phase, will be supported for tracking, telemetry and telecommand by additional ESTRACK ground stations as well as, possibly, Svalbard and Troll.

All routine payload operations will be preplanned and executed according to the Flight Operations Plan (FOP). Payload operations as well as science data downlink activities will be scheduled for autonomous execution on board based on the spacecraft position along the orbit. There are no real-time platform operations foreseen other than near real-time interactive activities at the time of commissioning (initial equipment turn-on, calibration), when uploading regular orbit maintenance manoeuvres or during contingency situations.

The ground stations - Kiruna, Svalbard

Kiruna station

For real-time housekeeping telemetry downlink and telecommanding during routine operations, Aeolus is expected to use ESA's ESTRACK ground station in Kiruna. The TC link (uplink) at 2030 MHz (S-band) will be at 2 Kbps, while the housekeeping TM downlink at 2205 MHz (S-band) will be at 8 Kbps.

For science data reception, Svalbard will be used, with science data received using 8040 MHz (X-band) at 10 Mbps. Additional X-band stations might also be used.

Ground segment & mission control system

This mission uses SCOS-2000

The major functions of the ground segment are to monitor and control the satellite, including the payload and the ground-segment elements; receive the instrument data from the satellite; and, to process, disseminate and archive the data and products, and provide for their retrieval.

The Aeolus ground segment at ESOC will use the latest version of the SCOS-2000 mission control system (version 5).

For the complete mission duration (launch up to the end of mission, when ground contact to the spacecraft/payload is terminated), facilities and services will be provided to the Payload Data Segment (PDS) located in ESA/ESRIN for planning of scientific data acquisition. This will include the uplink of instrument operation time lines as well as the provision of scientific data downlink schedules based on the predicted spacecraft orbit. The PDS will be responsible for measurement data acquisition via the X-band station network, the preprocessing of scientific data, and the scientific data archiving and distribution to the Meteorological Centres and general scientific community.

The Flight Operations Control Centre will operate from a Dedicated Control Room at ESOC. Data processing will be done at ESA/ESRIN, Italy, while wind profile retrieval will be done by the European Centre for Medium-Range Weather Forecasts (ECMWF), UK. Data ground processing will be completed within five minutes after reception.

The platform and payload

The platform

The satellite will have a dry mass of 1100 kg, comprising the satellite platform (650 kg, plus 116-266 kg propellant) and the payload (450 kg).

In launch configuration, the dimensions are: height 4.6 m, length 1.9 m, width 2.0m. The solar array will provide 2200 W power at end of life.

Attitude control will be maintained using reaction wheels, magnetotorquers and thrusters. On-board navigational and attitude sensors include a coarse Earth-Sun sensor, a magnetometer for coarse pointing control, a star tracker and an inertial measurement unit, as well as GPS for fine pointing control.

ADM-Aeolus payload components

The payload

Aeolus carries a single payload, the Atmospheric Laser Doppler Instrument (ALADIN), a Direct Detection Doppler Wind Lidar operating at near ultraviolet (UV) wavelengths (355 nm). It comprises two main assemblies:

• Transmitter: diode laser pumped Nd: YAG laser, frequency tripled to 355 nm at 150 mJ pulse energy, 100 Hz pulse repetition
• Receiver: 1.5 m diameter SiC telescope, Mie channel (aerosol and water droplets) with Fizeau spectrometer, Rayleigh channel (molecular scattering)

ALADIN is an active instrument which fires laser pulses toward the atmosphere and measures the Doppler shift of the collected return signal, backscattered at different levels in the atmosphere.