Minimize Heritage Missions

The SENTINEL-4 mission builds upon the heritage of a series of spectrometer instruments which have been or are currently measuring atmospheric properties since 1995; namely:

  • the Global Ozone Monitoring Experiment (GOME) on ESA's ERS-2 satellite which operated between 1995 and 2011.
  • the GOME-2 instrument on-board EUMETSAT's MetOp-A satellite, launched in 2006, still in service. A second GOME-2 is operating since 2012 on MetOp-B.
  • the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) instrument onboard ESA's Envisat mission which operated between 2002 and 2012.
  • the Ozone Monitoring Instrument (OMI) instrument onboard NASA's AURA spacecraft, operating since 2004 and still in service.
  • the Tropospheric Ozone Monitoring (TROPOMI) instrument onboard ESA's SENTINEL-5P spacecraft expected to be launched in 2016.

 

As shown in table 1, among these five heritage instruments, the one which has the best global performances (e.g. spatial resolution, Signal-to-Noise Ratio, spectral coverage) is TROPOMI as it reunites several of the best characteristics of its predecessors, even going beyond them like for example an unprecedented on-ground spatial resolution of 7 x 7 km.

All SENTINEL-4 heritage missions are passive backscatter spectrometers operating in Low Earth Orbits (LEO) which allow performing Earth global coverage measurements with a daily revisit time.

SENTINEL-4 on the other hand will be the first imaging spectrometer instrument which will be embarked on-board a satellite in a geostationary (GEO) orbit.
The GEO orbit, although limiting the geographic coverage (for SENTINEL-4 only to Europe and parts of North Africa and the Atlantic), will allow for the first time an extremely frequent (about 1hr) delivey of accurate atmospheric data: twenty to hundred times better  than the LEO missions.

In terms of spatial sampling, SENTINEL-4 will be roughly equivalent to SENTINEL-5 and SENTINEL-5P.
The wide spectral range covered by SENTINEL-4 is narrower as compared to SENTINEL-5 and SENTINEL-5P, and has been chosen to cover the signatures of fast varying tropospheric constituents.
The main characteristics of the five heritage instruments are summarised in Table 1 .

Instrument

Technical Concept

Spectral Range

Spatial resolution (km x km)

Earth Coverage

Revisit time

Operational

GOME

Whisk-broom (scanning)

UV-VIS-NIR (240-790 nm)

320 x 40

Global

1 ½ day

1995-2011

GOME-2

Whisk-broom (scanning)

UV-VIS-NIR (240-790 nm)

80 x 40

Global

1 ½ day

2006-present

SCIAMACHY

Whisk-broom (scanning)

UV to SWIR (240-2400 nm)

30 x 215

Global

6 days

2002-2012

OMI

Push-broom (staring)

UV-VIS (270-500 nm)

13 x 24

Global

1 day

2004-present

TROPOMI

Push-broom (staring)

UV-VIS-NIR-SWIR (270 – 2385 nm)

7 x 7

Global

1 day

Launch scheduled in 2016

SENTINEL-4/UVN

Push-Broom (scanning)

UV-VIS-NIR (305- 775 nm)

8 x 8

Europe + parts of North Africa and the Atlantic

1 hour

Launch scheduled  in 2021

Table 1: Main Characteristics of SENTINEL-4 and of its Heritage Instruments.