ENVISAT

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ENVISAT

• Burcu Bölükbasi

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Overview

• Introduction
• Mission and System
• History

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Introduction

• Launched by the European Space Agency in March,
  2002.
• Measurements of the atmosphere, ocean, land, and
  ice.
• Continuity of the data measurements of the ESA
  ERS satellites.

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• Earth science research
• Monitoring of the evolution of the environmental
  and climatic changes
• Development of operational and commercial
  applications

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Mission and System

• The Envisat Space Segment (the satellite itself)
  including the Polar Platform (PPF) and the
  payload
• The Envisat Ground Segment consisting of the
  payload data segment (PDS) and the flight
  operation segment (FOS)

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ARTEMIS(Advanced Relay and Technology Mission
Satellite)

• Testing
• Operating

New technology systems
Launched on 12 July 2001.
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• Explore advanced technology to transmit data
  directly from one satellite to another
• Observation satellites in low orbit like ERS must
  use on-board recording and global networks of
  ground stations

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• Two payloads for communications directly between
  satellites
• Receive data from low-Earth orbiting satellites
• Transmit them directly to Europe
• L-band land mobile payload allows two-way
  communications, via satellite, between fixed
  Earth stations and land mobiles - trucks, trains
  or cars - anywhere in Europe and North Africa.

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• ARTEMIS Coverage
• High and low rate data, including recorder
  playback, can be received under the Artemis
  coverage (the on-board Ka-band transmit terminal
  and data reception with the User Earth Terminal
  (UET) at ESRIN).
• The establishment of the link between the Envisat
  and Artemis satellites may require up to 3
  minutes.

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The Ten-thousandth Orbit

• The satellite completed its 10,000th orbit in 28
  January 2004.
• Traveled 450 million kilometers since its launch
• Envisat was using all its ten instruments to
  gather information about the earth and the ground
  segment was generating about 10,000 Megabytes of
  data products.

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• SCIAMACHY total ozone column
• Instrument Scanning Imaging Absorption
  Spectrometer for Atmospheric Chartography
  (SCIAMACHY)
• Date of Acquisition 28 January 2004
• Orbit number 10000
• Orbit direction Descending
• SCIAMACHY product used Level 1 spectra

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• ASAR Global Monitoring Mode over Arctic Sea,
  north of Greenland
• Instrument Advanced Synthetic Aperture Radar
  (ASAR)
• Date of Acquisition 28 January 2004
• Orbit number 10000
• Orbit direction Descending
• ASAR features Global Monitoring Mode image (1000
  meter resolution)
• ASAR mode Global Monitoring Mode (400 km wide)
• ASAR polarization HH

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Synthetic Aperture Radar (SAR) Technical
Information Instrument Synthetic Aperture
Radar (SAR) Dates of Acquisition Red 15 July
2004, Green 6 May 2004, Blue 22 January 2004
Orbit numbers 48286, 47284, 45781 Frame 2781
Instrument features 25 meter resolution
Coordinates NE Lat/Long N 41.30 / E 29.86 NW
Lat/Long N 41.48 / E 28.71 SW Lat/Long N 40.58
/ E 28.46 SE Lat/Long N 40.40 / E 29.60
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MERIS (Medium Resolution Imaging
Spectrometer) Technical Information
Instrument Medium Resolution Imaging
Spectrometer (MERIS) Date of Acquisition 18
November 2004 Orbit number 14218 Instrument
features FR Coordinates NE Lat/Long N 42.47 /
E 30.42 NW Lat/Long N 43.99 / E 23.56 SW
Lat/Long N 38.22 / E 21.63 SE Lat/Long N 36.79
/ E 27.97
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Advanced Synthetic Aperture Radar
(ASAR) Technical Information Instrument
Advanced Synthetic Aperture Radar (ASAR) Dates
of Acquisition Red 07 June 2004, Green 06
October 2003, Blue 15 December 2003 Orbit
Direction Descending Orbit number 11870, 8363,
9365 Instrument features Wide Swath Mode
(geometric sampling 1 pixel75 m.) ASAR
polarisation VV Coordinates  NE Lat/Long N
42.52 / E 31.00 NW Lat/Long N 42.51 / E 26.52
SW Lat/Long N 40.01 / E 26.59 SE Lat/Long N
40.03 / E 30.54
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• ASAR wide Swath Mode over Antarctica, the Ross
  Sea and giant iceberg B15-A
• Instrument Advanced Synthetic Aperture Radar
  (ASAR)
• Date of Acquisition 28 January 2004
• Orbit number 10000
• Orbit direction Descending
• ASAR features Wide Swath Mode image (150 meter
  resolution)
• ASAR mode Wide Swath Mode (400 km wide)
• ASAR polarization HH

http//www.esa.int/esaCP/SEMCPWWLDMD_FeatureWeek_0
.html
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• MERIS Reduced Resolution over Texas and Mexico
• Instrument Medium Resolution Imaging
  Spectrometer (MERIS)
• Date of Acquisition 28 January 2004
• Orbit number 10000
• Orbit direction Descending
• Instrument features Reduced Resolution image
  (1200-metre resolution)

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• AATSR Thermal Image over Baffin Island
• Instrument Advanced Along Track Scanning
  Radiometer (AATSR)
• Date of Acquisition 28 January 2004
• Orbit number 10000
• Orbit direction Descending
• Instrument features Level1b (TOA) image (1
  kilometre-scale resolution)

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OPERATIONS

• Envisat flies in a sun-synchronous polar orbit of
  about 800-km altitude.
• The repeat cycle of the reference orbit is 35
  days
• Provides a complete coverage of the globe within
  one to three days
• MWR and RA-2
• ERS-1 and ERS-2

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Mission and Operation Requirements

• Sun-synchronous polar orbit (SSO) Nominal
  reference orbit of mean altitude 800 km, 35 days
  repeat cycle, 1000 AM mean local solar time
  (MLST) descending node, 98.55 deg. inclination.
• The orbit is controlled to a maximum deviation of
  /- 1 km from ground track and /- 5 minutes on
  the equator crossing MLST.
• Recording of payload data over each orbit for low
  bit rate (4.6 Mps) on tape recorders or solid
  state recorder (SSR).
• High rate data (ASAR and MERIS) to be accessible
  by direct telemetry or recording on SSR.

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Global Low Rate Mission and Data Recovery
Strategy

• General operation concept
• continuous operation of the low-rate instruments
  around the orbit (with the exception of MERIS,
  which is limited by sun-illumination conditions)
  
• on-board recording of all instrument data
• data-recorder playback at least once per orbit in
  order to ensure availability of fast delivery
  products within less than three hours from
  observation
• systematic processing of all acquired data.

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Processing and Data Distribution Strategy

• Low-rate data is systematically processed on the
  ground and disseminated to users in near real
  time (NRT).
• All data is reprocessed off-line. Nominal
  off-line distribution is performed on physical
  media to registered users.
• Small products are available for retrieval on
  line, with the possibility for users to extract
  partial data sets.

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Regional Mission Operations and Data Decovery
Strategy

• The regional mission includes the full-resolution
  mode of MERIS and all modes of the ASAR, with the
  exception of the wave mode. The following
  sections provide the basic concepts ruling the
  operations of the regional mission.

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ASAR general operation strategy

• ASAR offers, by exploiting the combinations of
  polarizations and incidence angles, 37 different
  and mutually exclusive operating modes in high,
  medium (wide swath mode), and reduced (global
  monitoring mode) resolution.
• ASAR high- and medium-resolution imaging modes
  are either transmitted on a real time link
  (direct X-band or via Artemis Ka-band link) or
  recorded on the on-board solid state recorder for
  ground data recovery.

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ASAR processing and data distribution

• Browse products are available on-line.
• High-resolution products are processed in near
  real time or off-line, upon user request.
• All medium (and high) resolution products are
  delivered to users on request either in near real
  time on a dissemination channel or off line on
  physical media.

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MERIS general operation strategy

• MERIS operates at full resolution (FR with 300 m
  resolution at nadir).
• The data are averaged on board to produce a
  separate data stream at reduced resolution (RR
  with 1200 m resolution at nadir).
• MERIS FR is either transmitted on a real time
  link (direct X-band or via Artemis Ka-band link)
  or recorded on the on-board solid state recorder
  for ground data recovery.

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MERIS processing and data distribution

• MERIS RR data acquired at ESA facilities is
  systematically processed in near real time to
  generate MERIS RR Level 1b and 2 products as well
  as browse products.
• Browse products are available on-line.
• Upon user request MERIS FR data is processed and
  distributed either in near real time
  (dissemination link) or off-line (physical media).

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Regional mission data recovery

• data over Europe will be acquired directly via
  X-band links (Kiruna and Matera coverage),
• data outside Europe will be acquired whenever
  possible via Artemis direct transmission to the
  UET located at ESRIN,
• data outside direct coverage of the ESA X-band
  stations and Artemis, will be recorded on board
  using the SSR and acquired via deferred dump to
  one of the ESA stations via X- or Ka-band links,

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• data requested by a station operator or by the
  distributing entities on behalf of a station
  operator will be transmitted in X-band for
  acquisition by the corresponding station,
• if data to be acquired by a station operator are
  also needed as part of ESA archive, then in
  parallel with X-band direct data transmission,
  ESA will acquire the data via combined use of the
  SSR, X- or Ka-links as appropriate.

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On-board Recording Capability

• The on-board recording system is composed of two
  solid state recorders (SSR) with 70 Gbits
  capacity each, and one tape recorder (TR), 30
  Gbits capacity as back up for low rate data
  recording.

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Main technical characteristics of the SSR's
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Tape Recorder

• One tape recorder (TR) onboard ENVISAT capable of
  recording the low-rate global data.
• The recorder allows to record up to 6500 seconds,
  which is slightly more than one full orbit of LR
  data recording.
• The TR playback dump is performed at 50 Mbps
  (half-RF channel) via X- or Ka-band links.

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On ground data recovery (data dump)

• Two selectable data dump rates are usable on
  X-band and/or Ka-band RF-channels
• 50 Mbps (half RF channel) dump of 70 Gbits in 23
  min 20 sec.
• 100 Mbps (full RF channel) dump of 70 Gbits in 11
  min 40 sec. (for ASAR HR data only).
• Each of the three memory areas can be separately
  controlled with respect to data dump time and
  data rate.

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Operation strategy and mission impact

• One SSR will be used for the global mission, for
  low rate data recording.
• Second SSR will be used for the regional mission
  (ASAR HR and MERIS FR), with data dump via
  ARTEMIS to the user Earth terminal (UET).

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Data transmission

• up to two X-band links operating at a time
• up to two Ka-band links operating at a time
• X- and Ka-band transmitters operate
  independently, therefore up to two X-band links
  and two Ka-band links can be operated
  simultaneously.

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Mission Scenarios
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Global mission scenario

• continuous operation of the low-rate instrument
  around the orbit (For MERIS, sun-illumination
  constraints limit the observation to about 43.5
  minutes per orbit)
• on board recording of all instrument data
• playback at least once per orbit to ensure
  availability of FD products within less than
  three hours from observation
• systematic processing of all acquired data.

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Regional mission scenario

• the ASAR high-rate operations in wide-swath mode
  and narrow-swath modes
• the MERIS full-resolution (FR) mode

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The Envisat Orbit
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Measurement patterns orbital parameters
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Orbit selection
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Orbit maintenance

• The orbit maintenance requirements are that the
  deviation of the actual ground track from the
  nominal one is kept below 1 km and that the mean
  local nodal crossing time matches the nominal one
  to better than five minutes.
• The orbit maintenance strategy aims for minimum
  disturbance of the payload operation.

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 History

• The development of a multimission Polar Platform
  for future Earth observation missions, initially
  started as an element of the Columbus Space
  Station Programme.
• The Polar Orbiting Earth Observation Mission
  (POEM-1), initially conceived as a combined
  mission with instruments for scientific
  application, research, and operational
  meteorology. This mission, to be based on the
  Polar Platform, was to be the successor of ERS.

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The Polar Platform (PPF)

• deletion of multimission requirements and related
  activities for cost saving reasons
• splitting of the first mission POEM-1 into
  Envisat (the environmental mission) and METOP-1
  (the meteorological mission) in mid-1993
• several iterations on cost savings/descoping
  actions executed in mid-1993, early 1994, and the
  end of 1995 to reduce overall programme costs in
  industry and ESA

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The mission

• The development of the payload instruments for
  Envisat started after the split of POEM-1 into
  Envisat and METOP-1 at the Ministerial ESA
  council meeting in December 1993.

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Objectives
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Primary Objectives

• to provide for continuity of the observations
  started with the ERS satellites, including those
  obtained from radar-based observations
• to enhance the ERS mission, notably the ocean and
  ice mission
• to extend the range of parameters observed to
  meet the need of increasing knowledge of the
  factors determining the environment
• to make a significant contribution to
  environmental studies, notably in the area of
  atmospheric chemistry and ocean studies
  (including marine biology).

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Secondary Objectives

• to allow more effective monitoring and management
  of the Earth's resources
• to better understand solid Earth processes.

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Global mission objectives

• Real time data delivery (from a few hours to one
  day from sensing)
• forecasting of the sea state conditions at
  various scales
• monitoring of sea surface temperature
• monitoring of some atmospheric species (e.g.,
  ozone for warning purposes)
• monitoring of some atmospheric variables (e.g.,
  temperature, pressure, and water vapor, cloud top
  height, earth radiation budget, etc.)
• monitoring of ocean color for supporting
  fisheries and pollution monitoring (complementing
  the regional mission).

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• Off-line mode (days to weeks from sensing)
• radiate processes
• ocean-atmosphere heat and momentum exchange
• interaction between atmosphere and land or ice
  surfaces
• composition of the atmosphere and associated
  chemical processes
• ocean dynamics and variability
• ice sheet characteristics and sea ice
  distribution and dynamics
• large-scale vegetation processes in correlation
  with surface energy and water distribution
• primary productivity of oceans
• natural and man-made pollution over the oceans.
• support to large international programmes (GCOS,
  IGBP, etc.).

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Regional mission objectives

• sea ice off-shore applications
• snow and ice detection and mapping
• coastal processes and pollution monitoring
• ship traffic monitoring
• agricultural and forest monitoring
• soil moisture monitoring and large-scale
  vegetation processes
• geological features and mineral resources
• application linked to SAR interferometry (DEM
  generation, hazard monitoring, etc.)
• hydrological research and applications
• support to fisheries in coastal waters

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Instrument contribution to Envisat mission
objectives
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• http//envisat.esa.int/
• http//www.temis.nl/
• http//www.esa.int/artemislaunch/
• http//www.esa.int/artemislaunch/videos/videos.htm
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• http//earth.esa.int/isc/white.pl?map.x249map.y
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• http//earth.esrin.esa.it/isc/white.pl?map.x233m
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• http//www.esa.int/esaCP/SEMCPWWLDMD_FeatureWeek_0
  .html

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ENVISAT

• Burcu Bölükbasi