This Echo is READ ONLY !   NO Un-Authorized Messages Please!
 ~~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2\28 ESA - Envisat celebrates first anniversary in space
Part 1 of 2

European Space Agency

Press Release

Envisat celebrates first anniversary in space
=============================================
28 February 2003

One year ago tonight, the largest and most sophisticated Earth
observation satellite ever built blazed a fiery trail into the night
skies above French Guiana and became another bright star in the
constellation of spacecraft in ESA's Earth observation programme.

The spacecraft, dubbed Envisat for Environmental satellite, carried
with it a suite of 10 advanced sensors designed to provide scientists
on the ground with the most comprehensive look ever offered by a
remote-sensing satellite of the Earth's oceans, land, atmosphere and
ice caps.

Borne aloft by an Ariane-5 launcher, the picture-perfect launch of
Envisat from the Europe's spaceport in Kourou was followed by a
flawless insertion into a sun-synchronous polar orbit. Since reaching
its final orbital position on 3 April, Envisat has circled the globe
approximately 58000 times in an endless circle that allows it to fly
over the same area on Earth every 35 days.


All instruments fully operational
---------------------------------
Following the successful launch and insertion into orbit of Envisat,
the proudest accomplishment of the Envisat team is that all 10
instruments are operating as planned.

This assessment came after a long and complex commissioning phase of
the satellite, centred on ensuring that all ten instruments onboard
Envisat were working properly. This task was complicated by multiple
operating modes for many of the sensors. For example, the imaging
radar, ASAR, works in five different modes and 37 different sub-modes.

As part of this process, the instruments also need to be calibrated,
with the measurements and other observations recorded by Envisat's
sensors matched against the results from other satellite, airborne and 
ground-based instruments. Well worth the effort, the calibration work 
sees to it that the Envisat mission returns the highest quality of 
reliable, accurate data possible back to researchers on Earth. 

These calibration and validation procedures for each of the Envisat
instruments occupied the Envisat team and outside researchers brought
in to assist for most of last year. Several updates to the onboard
instrument software were installed to correct for a few anomalies that 
were encountered. A calibration review in September confirmed that the 
satellite and instruments were operating nominally, with stable 
performances seen from all of them. 

The late arrival of Artemis to its proper orbital slot (see related
articles) forced Envisat to rely exclusively on the earth station in
Kiruna, Sweden. This produced an extremely high workload, and slowed
the pre-processing and distribution of Envisat data. To compensate, at 
least partially, ad hoc transmit and receive equipment was installed 
in November at another earth station at Svalbard, the Norwegian 
archipelago close to the North Pole. This improved the performance of 
the ground segment while the Envisat team has started the testing 
activities with Artemis that are now underway and expected to be 
completed this spring.

ESA technicians encountered a related difficulty with Envisat's
Payload Data Segment (PDS), the ground data delivery network for data. 
Initial performance of the PDS was not reliable enough to maintain the 
original schedule for delivering data products to the instrument teams 
involved in the calibration and validation activities. A number of 
corrective actions were taken, including new releases of the PDS 
subsystems and new operational procedures, which allowed the gradual 
opening of the Envisat data services to users during the fourth 
quarter of last year. 


Envisat enters initial operational phase
----------------------------------------
Once Earth imagery and other data acquired by Envisat's sensors is
transmitted to ground stations, it is still a long way away from being 
usable by scientists and other researchers studying various aspects of 
the Earth's environment. The data still must be turned into either 
calibrated engineering values, and then into validated geophysical 
products. This was the task of the calibration/validation teams which, 
despite the initial ground segment difficulties, received enough data 
to provide results for the formal instrument and product reviews 
conducted in September and December. 

"This confirmed the enthusiasm of the Earth science community for the
initial results of the Envisat instruments," said Prof. José Achache,
ESA Director of Earth Observation.

Based on the results of the calibration/validation reviews of Envisat, 
the commissioning phase of the mission was closed at the end of 2002, 
and ESA formally authorised the transition of Envisat into the initial 
operations phase.

Of the more than 800 potential Envisat scientific projects worldwide,
500 can now request ASAR or MERIS products, a significant milestone
for two major Envisat instruments. A total of 73 products have been
released gradually since September 2002 and made available in a
variety of technical "flavours" and distributed via different media
such as the Internet, satellite link, CD-ROM, Exabyte data packs, and
soon, DVD. 


Ten eyes on natural and man-made events
---------------------------------------
Throughout the past 12 months, Envisat has captured people's
imaginations and media headlines all over the world by returning
striking images and valuable scientific data of the events, both
natural and man-made, that have helped to shape our world. Some of the 
most notable of these include:

* the 150-km-long oil slick from the sinking oil tanker, Prestige, 
  captured by Envisat's ASAR sensor in November, which vividly 
  captured the extent of the spill off the Spanish coast; 

* ASAR images of the August floods along the Elbe River valley in
  Germany, Austria and the Czech Republic, provided to governmental 
  authorities and civil relief agencies under the International 
  Charter on Space and Major Disasters; 

* the birth of a new iceberg in the Antarctic through a series of
  images captured by Envisat from May through October;

* spectacular MERIS images showing the October eruptions of Mount Etna 
  in Sicily, and phytoplankton blooms in the oceans near Canada, 
  Norway and Senegal. 

Other imagery and measurements from the spacecraft's sensors may not
have been as visually striking, but were of great interest to the
Envisat research community. Not only were the eruptions of Mount Etna, 
for instance, recorded by the MERIS optical and infrared spectrometer, 
follow-on analysis of data from the SCIAMACHY instrument showed the 
levels of sulphur dioxide gases thrown up by the volcano and carried 
by winds towards Africa and the eastern Mediterranean. In another 
example, data from Envisat's GOMOS sensor was used in conjunction with 
data from other ESA satellites to predict accurately the premature 
breakup of the ozone hole in September, months earlier than normal.


(continued)

---