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Mission Concept

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.

International Collaboration

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.

1 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.

Figure 1: CLARREO Baseline Mission

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.

Figure 2: CLARREO Minimum Mission

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.

Figure 3


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.

Mission Option Relative Science Value Cost Estimate ($RYM)
MCR Baseline Mission: 6 Instruments, 4 Smaller or 2 Larger SC in 2 P90 orbit. 100% ~ $800
+ Launch Vehicle
MCR Minimum Mission: 3 Instruments, one SC in a single P90 orbit 62% ~ $675
+ Launch Vehicle
ISS Mission Concept: 2 Instruments on ISS, RO data from COSMIC 73% ~ $400
Includes Launch Cost
EV-2 ISS full cost guidelines