Mission Concept Overview
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission enables highly accurate decadal
change observations traceable on-orbit to SI standards, for knowledge of uncertainty and comparison with
future measurements. The CLARREO Project demonstrated readiness to begin Phase A at a fully successful
Mission Concept Review in November 2010. Due to NASA budget considerations, CLARREO remains in an extended
pre-Phase A with a launch readiness date of no earlier than 2023. NASA continues to fund efforts to
refine the mission design and to examine alternative platforms, such as the International Space Station (ISS),
focusing on lower cost implementation while achieving a majority of the CLARREO science objectives.
The CLARREO Science Definition Team (SDT) was selected in January 2011 and has made
considerable progress in advancing the rigor of climate Observing System Simulation Experiments (OSSEs),
defining the complementary applications of CLARREO IR, RS, and GNSS-RO observations for climate signal
benchmarking and climate model testing, advancing the procedures for reference intercalibration,
and in assessing the stability of climate retrievals. For additional information, please refer to the Science tab.
The CLARREO team continues to explore potential opportunities for international collaboration1.
They have been collaborating with two mission proposal groups in Europe: the Traceable Radiometry
Underpinning Terrestrial and Helio Studies (TRUTHS) mission for high-accuracy solar reflected spectra,
and the Far Infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission for high-accuracy
thermal infrared spectra. Both of these missions are very complementary to CLARREO.
When flown as two separate platforms during the same time frame, they can provide an international
climate benchmark and calibration constellation. Specifically, overlapping flights provide the
opportunity for in-orbit comparisons of climate signals from the TRUTHS and CLARREO reflected solar
spectrometers and the far-infrared portion of the CLARRRO IR spectrometer, increasing confidence
in the results through independent verification. This independent verification is especially
key to producing data records that will be used to benchmark climate change for future policy decisions.
When flown on a single platform, collaboration has the potential to reduce the overall costs to NASA
and establish the climate record sooner.
The U.K.ís National Centre for Earth Observation (NCEO) and NASA signed a Letter of Agreement in support of CLARREO.
The studies within the UK involve the investigation of detectable signatures of climate change in
the infrared spectrum of the Earth, based on the analysis of real atmospheric spectra, measured by past
or current satellite instruments. These studies complement and augment at no cost the NASA-funded Pre-Phase A
studies designed to define rigorous science and instrument requirements for CLARREO.
Potential Mission Concepts
The team has evaluated multiple implementation options for achieving the CLARREO mission.
The goal of these studies is to provide NASA with a potential trade space of lower cost options
linked to the relative science value to inform decision making.
CLARREO Baseline Mission
The CLARREO Baseline Mission achieves 100% of the science by flying 6 instruments
(i.e., 2 copies of the IR, RS, and RO) in two 90° inclination polar orbits. This orbit choice is well-suited
to CLARREO's requirements and assures full diurnal cycle sampling for spectral fingerprints as well as full
reference inter-calibration sampling over all climate regimes and all satellite orbit thermal conditions.
This concept was presented to the CLARREO Mission Concept Review Board in 2010, where the board confirmed
that the approach was technically/programmatically feasible and met the mission objectives.
CLARREO Minimum Mission
The CLARREO Minimum Mission with 3 instruments in a single 90° inclination polar orbit could achieve 62% of the Baseline Mission science at a significantly reduced cost.
CLARREO ISS Mission
A mission concept to fly two CLARREO instruments, RS and IR spectrometers,
on the International Space Station (ISS) as shown in in the figure to the left.
Because of the higher reliability of the ISS as a spacecraft, thereby allowing a longer climate record,
this option offers the best overall science value of 73% for the lowest cost (see Table below). Due to the ISS inclination orbit,
CLARREO will not have coverage of Earth's polar regions, however, flying in a precessing orbit will significantly
enhance sampling for inter-calibration of existing sensors. In this mission option, the radio occultation
data is acquired from the COSMIC constellations.
Included in this table are the three CLARREO Mission Concept Options described above, including their relative science value and cost estimate in real year dollars.
||Relative Science Value
||Cost Estimate ($RYM)
|MCR Baseline Mission: 6 Instruments, 4 Smaller or 2 Larger SC in 2 P90 orbit.
+ Launch Vehicle
|MCR Minimum Mission: 3 Instruments, one SC in a single P90 orbit
+ Launch Vehicle
|ISS Mission Concept: 2 Instruments on ISS, RO data from COSMIC
Includes Launch Cost
EV-2 ISS full cost guidelines