Key stages in the ordering and delivery process
Before being delivered in exploitable form, SPOT scenes
or value-added products go through a number of stages to ensure that they
satisfy customer requirements.
The 9 stages are:
- The on-line SPOT product catalogue
- Customer acquisition request
- Programming request
- Satellite programming and stationkeeping
- Image reception
- Inventorying and archiving
- Image validation and completion of the programming sequence
- Product processing
- Delivery to the customer
1. The
on-line SPOT product catalogue
Any user wanting to obtain SPOT imagery can browse Spot Image's on-line
catalogue on the Internet http://www.spotimage.fr
. This catalogue contains five million archived scenes selected from the ten
million acquired since 1986 when the first SPOT satellite was launched. Newly
acquired imagery is added to the archive every day. The catalogue lets users
view all existing scenes of their area of interest, display information about
a scene (cloud cover and acquisition date, for example), find details about
off-the-shelf products, send queries and ask for a quotation.
· The product catalogue is now updated a lot more often, as new SPOT
scenes will be entered just one hour after acquisition.
· Cloud cover ratings, calculated manually until now, will be determined automatically
by an algorithm. This algorithm uses a cloud mask to determine the position
of clouds in a scene a lot more precisely.
· Customers will now be able to order SPOT sub-scenes (quarter scenes, one-eighth
scenes or a specific area selected in the catalogue) to keep file sizes down.
A full SPOT 5 scene may exceed 600 Megabytes, depending on the processing
level, and will be four to 16 times larger than scenes from the other SPOT
satellites.
2. Customer acquisition
request
In some cases, customers may have specific requirements
that the catalogue cannot fulfil. For example, they may want more recent imagery
of an area of interest, the full benefits of SPOT 5's improved resolution,
full coverage of an entire territory to very precise specifications, or future
image acquisitions for crop monitoring. Spot Image offers a custom image acquisition
service for this very purpose. The satellite programming team analyses the
customer's request and determines its feasibility.
In the last 16 years, Spot Image's programming team
has developed a methodology and expertise unequalled anywhere in the world.
And the SPOT system also offers users unique capabilities compared with one-metre-resolution
systems. The SPOT satellites' twin imaging instruments cover a ground swath
of 120 kilometres-almost ten times more than very-high-resolution satellites.
·
Thanks to the HRS instrument and the new Supermode sampling concept, SPOT
5 affords greater acquisition flexibility and new viewing combinations. Like
its predecessors, SPOT 5 can downlink two images simultaneously but it can
also store an extra three images in memory. The programming team manages all
these combinations to make the best use of acquisition capacity.
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3. Programming request
A programming request defines when and where imagery
is to be acquired, and specifies spectral bands, viewing angles and so on.
These parameters are adjusted by the Programming Centre, or CPR, which manages
all current programming requests on a daily basis and resolves programming
conflicts.
SPOT
5's HRS instrument will optimize stereopair acquisition programming. Because
HRS has two telescopes, one pointing forward and one aft of the satellite,
it can acquire two images of the same ground strip just one minute and 30
seconds apart. It thus covers a very wide area-600 kilometres by 120 kilometres-in
a single pass. Stereopair images are then used to generate digital elevation
models (DEMs) for relief mapping. HRS will enable large-scale production of
high-quality DEMs providing a precise picture of terrain elevation vital for
a broad range of applications-including low-altitude flight simulations and
cellular phone network planning-and for automatic production of orthoimages.
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The CPR - a powerful planning tool The CPR has the capability to:
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4. Satellite programming and stationkeeping
Every morning, the CMP uplinks the daily workplan containing telecommands
for each satellite via stations in CNES's 2-GHz network, such as that at Issus-Aussaguel
near Toulouse. Each satellite receives and stores in memory a complete sequence
of acquisition instructions for the coming day. Every day, an operational
coordination team meets to check the status of satellite subsystems and determine
operations for the days ahead.
To
reduce operating costs, the SPOT 5 system has been designed so that it can
be operated during office hours. For previous SPOT satellites, the CMP was
staffed by shifts of engineers and controllers working round the clock, seven
days a week.
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The SPOT satellites under close surveillance
A ground engineer, a spacecraft engineer and a mission and operations engineer are on call outside office hours, ready to respond within the hour. If required, CNES development teams and engineers working for major contractors provide additional technical support.
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5. Image reception
The satellites acquire imagery according to their daily workplan. They then
transmit real-time image telemetry to ground if within range of a direct receiving
station, or store images for later downloading.
· To
speed up image reception and enhance satellite programming, a compact receiving
station with a 3.5-metre antenna, called Easy Link to SPOT (ELS), has been
set up at Spot Image's Toulouse facility to replace the Issus-Aussaguel station,
which has a 10-metre antenna. The ELS station is linked to Spot Image's data
processing centre.
6. Inventorying and archiving
As soon as a station receives data from the satellites, it sends them electronically
to the Archive and Preprocessing Centre, or CAP, at Spot Image. Here, they
are immediately inventoried and archived on digital storage media and automatically
listed in Spot Image's catalogue.
· The inventorying process has traditionally involved inspecting scenes
visually to assess cloud cover. Now, this task will employ automatic algorithms
to create and store cloud masks in the catalogue.
· To standardize and optimize the system, direct receiving stations
(DRSs) will progressively be equipped with a SPOT 5 Terminal. This is a standard
terminal derived from the system operating at Spot Image. This uniform platform
will allow receiving stations to play a more effective role in collecting
SPOT data and make it a lot easier for them to work together, since they will
be using the same resources, formats and operating procedures.
7. Image
validation and completion of the programming sequence
The programming sequence is completed at Spot Image, where the programming
team analyses acquired images one by one-checking radiometric quality, coverage
of the area of interest, acquisition date with respect to climatic conditions,
cloud cover and so on-to ensure that the customer's order has been fulfilled.
·
HRS stereopairs go through a special validation process involving teams at
IGN, France's national survey and mapping agency, to ensure that they are
suitable for generating accurate DEMs.
· Cloud masks created at the inventorying stage will also facilitate
validation, especially where customers require satellite imagemaps in a precise
mapsheet format.
8. Product processing
To fulfil customer orders, Spot Image generates standard products corrected
for radiometric errors caused by varying sensitivity of detectors in a sensor's
CCD array, and for geometric distortions caused by the satellite's motion
and viewing geometry. To make these corrections, the CAP relies on calibration
parameters supplied by the image quality centre at CNES (QIS).
·
Spot Image will provide level 2A products (rectified in a standard map projection
without using ground control points) offering a location accuracy of 50 metres,
rather than 500 metres until now. SPOT 5 is able to achieve this level of
accuracy thanks to its star tracker and to the DORIS precise-positioning system.
· Sophisticated processing techniques and powerful computer systems
will also be used to generate 2.5-metre-resolution images automatically.
· The HRS instrument will yield better, more accurate DEMs faster than
before.
· Automatic, large-volume production of orthoimages-previously considered
high-end, value-added products-will make them affordable and open up the market
for new users.
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CAP takes up the technical challenge |
9. Delivery to the customer
Once quality checks have been completed to ensure expected image quality,
preprocessed SPOT data are delivered to the customer on CD-ROM and soon on
line.
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Spot Image is gearing up to deliver products on line. To this end, SPOT 5
products are in a new international standard format called DIMAP (for Digital
Image Map), which encapsulates metadata in XML and images in GeoTIFF format.
XML was chosen because it is well suited to exchanging data over the Internet
and delivering network products, and is expected to become the platform of
choice for business-to-business exchanges in the years ahead. All Spot Image
products will be moving over to this new format from 2002 to make them easier
to use for a greater number of users. DIMAP will provide users very detailed
information describing the technical features of each image they browse. Ultimately,
they will be able to download satellite imagemaps with accompanying metadata.
Quality first
Spot Image has earned wide recognition for quality of service within today's
geographic information marketplace. Its sales and engineering teams work closely
with customers at all stages to ensure that their requirements are satisfied.
Spot Image achieved certification to the ISO 9001:2000 standard in 2001, becoming
the first European satellite data supplier to reach this milestone. Certification
covers the SPOT satellite data production process, and sales of geographic
information products and services, thus guaranteeing optimum quality.
