Summary of the WATS mission
Accurate observations of the present water vapour and temperature in the troposphere and stratosphere - including their variability - are highly important in climate change research (IPCC, 2001):
To monitor climatic variations and trends at different vertical levels and for each season. This to improve our understanding of the climate system as well as to detect the different fingerprints of global warming;
To improve the understanding of climatic feedbacks defining the magnitude of climate changes in response to given forcings;
To validate the simulated mean climate and its variability in global climate models;
- To improve/tune - via data assimilation - the parameterisation of unresolved processes in climate models and to detect inter-annual variations in external forcing of climate.
The main objectives of WATS are:
to establish a highly accurate and vertically resolved climatology of water vapour in the troposphere with global all-weather measurements of its concentration,
to establish a highly accurate and vertically resolved climatology of temperature in the troposphere and stratosphere with global all-weather measurements of its vertical profiles,
to support research on climate variability and climate change and on validation and improvement of atmospheric models,
to support advancements on NWP (Numerical Weather Prediction),
to support analysis and validation of data from other space missions,
- to demonstrate a novel active self-calibrating atmospheric sounding method.
Spin-off objectives of WATS are:
assessing and improving present attenuation models,
- ionospheric climate and weather and space weather investigations.
|Horizontal sampling||< 500 km|
|Vertical range||0-15 km for humidity|
|0-50 km for temperature|
|Vertical sampling||0.5-1 km|
|Temporal sampling||1-12 hr|
|Accuracy on humidity||< 0.025 g/kg rms|
|Accuracy on temperature||< 1 K rms|
|Spatial distribution||homogeneous over each day|
|Local times distribution||homogeneous over a few months|
|Mission duration||> 5 years|
Constellation of micro-satellites each of them carrying two instruments:
- a precision L-band receiver and related antennae for GNSS-LEO occultations
- a precision X/K-band transmitter / receiver and related antennae for LEO-LEO occultations (3 frequencies)
- Satellite operation and control
- Fiducial stations for Precise Orbit Determination
- Processing and archiving centre
- Science data centre for high level products generation and for data assimilation.
Profiles of refractivity and absorption, and retrieved profiles of water vapour, temperature and pressure as a function of height.
A substantial proportion of the products should be made available to data assimilation centres in near-real time.
12 micro satellites
– mass: ~150 kg
– power: ~100 W
- flying in a stable constellation optimising the quality of occultations,
- at two altitudes (~600 and ~800 km) to optimise the spatial distribution of occultation measurements,
- with drifting orbits to optimise the temporal (local time) distribution of occultation measurements.
Last update: 18 October 2001