Braving remorseless July temperatures, more than 40 researchers from across
Europe gathered at the hot, dry heart of Spain — a site selected because of the
unique opportunity to have three consecutive acquisitions over the area by
CHRIS, the high-resolution imager aboard ESA’s Proba.

The group was there to acquire a wealth of ground, air and space-derived data
simultaneously and in so doing help develop the next generation of Earth
Observation sensors.

Scientists from 11 institutions and five European countries gathered at the
Barrax test site, a scientifically well-characterised agricultural site in La
Mancha. Across three intensive and very long days between 12 and 14 July they
collected detailed in-situ measurements of their surroundings while airborne
sensors were flown overhead and several Earth Observation (EO) satellites
overpassed them.

Known as the Spectra-Barrax Campaign (SPARC), the co-ordinated acquisition of
ground, air and space data on a single landscape came about as part of the
preparatory study associated with Phase A of ESA’s planned Earth Explorer
mission Spectra.

Spectra is planned to carry a hyperspectral camera that can resolve light into
individual spectral bands at higher resolution than ever before. This camera
will be placed on a small agile platform to enable it to image its targets from
multiple angles. As a result it will return a wealth of information on land
cover mapping and the amount and condition of vegetation across the Earth’s surface.

"What SPARC provided for us is a unique opportunity to test and validate many
critical aspects of such a hyperspectral mission," said ESRIN Scientific
Campaign Co-ordinator Remo Bianchi. "These included the simulation of satellite
image products, the development and validation of retrieval algorithms that
transform the imaged scenes into maps of biophysical parameters and to test
methods for the correction of atmospheric effects in the images."

Working from half past six in the morning until nine at night, the teams flew
radio sondes attached to balloons to sample atmospheric data, measured solar
irradiance levels, used an experimental Lidar laser device to measure
atmospheric aerosols, and recorded vegetation characteristics in great detail.
Some 4000 Leaf Area Index samples were acquired, tree canopy properties were
measured from various different directions, and chlorophyll samples were taken.
And for added accuracy, detailed laboratory analysis of all 55 crops studied was
also later carried out.

Meanwhile the German Aerospace Centre DLR carried out high-resolution airborne
acquisitions using their experimental HYMAP and ROSIS sensors on 12 July,
simultaneously to ESA’s Proba spacecraft — with its 18-metre-resolution Compact
High Resolution Imaging Spectrometer (CHRIS) camera — making the first of three
overpasses in three days.

Proba is a technology demonstrator satellite launched in October 2001 that has
since had its lifetime extended as an Earth Observation mission, used for
environmental monitoring. The reason Barrax was chosen as a study site on these
three particular days was the coincidence of three consecutive days of Proba
overpasses. The satellite was launched into an orbit that allows coverage of a
given site for two or three consecutive days.

Other satellite sensors also successfully acquired pictures of the Barrax site
during the SPARC campaign. Envisat’s MERIS instrument imaged the site both in
reduced and full resolution, while the SEVIRI camera aboard the ESA-built MSG
also acquired images.

"The SPARC campaign was highly successful and able to provide observations at
the appropriate spatial, temporal, spectral and directional resolutions," said
Malcolm Davidson, also a Scientific Campaign Coordinator based at ESTEC. "The
data will serve as reference for many studies in the next few years to support
the development of future hyperspectral multi-angular sensors such as the Earth
Explorer Spectra mission."

The arduous task of organising and analysing all the data collected during the
campaign has started. First results will be presented in a progress meeting this
November in Valencia, Spain.

More information

* Proba

* About Spectra

* About Campaigns


[IMAGE 1:]
CHRIS/Proba image over Barrax site on 12 July 2003.

Credits: ESA

[IMAGE 2:]
An artist’s impression of Spectra.

[IMAGE 3:]
Launching an atmospheric radiosonde.

[IMAGE 4:]
Radiometric measurements over a corn field.