# Presentation: 129185

## CERES InstrumentOverview / Calibration

**CERES Instrument****Overview / Calibration**
**Kory J. Priestley**
**Climate Science Peer Review**
- NASA Langley Research Center
- June 5th, 2007

## Role and responsibilities of the CERES Instrument Working Group in the Radiation Sciences Program

CERES Instrument Overview

Radiometric Calibration Goals and on-orbit performance 

- CERES Instrument Overview
- Radiometric Calibration Goals and on-orbit performance

**Instrument Overview / Calibration**

## CERES DATA PROCESSING FLOW

**SNOW-ICE MAPS**
**ATMO STRUCTURE **
**AEROSOLS**

**CERES DATA PROCESSING FLOW**

**CERES CALIBRATION/**
**LOCATION**

**ERBE-LIKE**
**PRODUCTS**

**CERES DATA**
**TRMM, Terra, Aqua**

**CLOUD ID;**
**TOA/SURFACE FLUXES**

**ANGULAR**
**DISTRIBUTION**
**MODELS**

**TIME/SPACE**
**AVERAGING**

**CERES TIME AVERAGE**
**CLOUD/RADIATION**
**TOA, SFC, ATMOS**

**GEOSTATIONARY**
**DATA**

***3-hourly 1-degree grid***

***High level of data fusion; up to***
***11 instruments on 7 spacecraft ***
***all integrated to obtain climate***
***accuracy in top to bottom fluxes ~***
***8-dimensional radiative assimilation***

**CLOUD IMAGER**
**DATA**

**SOLAR ZEN.**
**ALBEDO**
**MODELS**

**CERES TOA &**
**SURFACE**
**PRODUCTS**

**LaRC Fu-Liou **
**RADIATIVE MODEL**

**GEOSTATIONARY**
**DATA**

***monthly 1-degree grid***

## 
Characterize and calibrate the instrument spectrally, spatially and radiometrically

Responsible for ensuring instrument performance is in consonance with all science objectives

Continually looking at ways to improve measurement technology to maximize scientific return

Long term goal is to minimize the dichotomy between science, engineering, and project management

- Characterize and calibrate the instrument spectrally, spatially and radiometrically
- Responsible for ensuring instrument performance is in consonance with all science objectives
- Continually looking at ways to improve measurement technology to maximize scientific return
- Long term goal is to minimize the dichotomy between science, engineering, and project management

**CERES Instrument Working Group**

## CERES Instrument

- Design is based upon the Earth Radiation Budget Experiment (ERBE) philosophy
- Instrument was designed, manufactured and tested        by TRW (Redondo Beach, CA)
- Contains three sensor assemblies with cassegrain    optics and thermistor bolometer detectors
- Sensors measure thermal radiation in the near-visible through far-infrared spectral region
- Three sensor channels are coaligned and mounted        on a spindle which rotates about the elevation axis
- Hemispherical sampling obtained with an azimuthal     axis drive system
- Calibration Accuracy Requirements - 0.5% LW, 1.0% SW

**CERES Instrument**

## Primary CERES Operational Modes

**Primary CERES Operational Modes**

## CERES Spectral Response Function

**Note:  LW****DAY**** = Total - Shortwave**

**CERES Spectral Response Function**

## Radiometric Performance Requirements

**Requirements per Ohring et. al. are more stringent than CERES by a factor of 3-5**

| Spectral Regions | Solar |  | Terrestrial |  | Atmospheric Window |
| --- | --- | --- | --- | --- | --- |
| Wavelengths | 0.3 - 5.0 m |  | 5.0 - 200 m |  | 8 - 12 m |
| Scene levels | <100 w/m2-sr | >100 w/m2-sr | <100 w/m2-sr | >100 w/m2-sr | All Levels |
| Accuracy Requirements | 0.8 w/m2-sr | 1.0 % | 0.8 w/m2-sr | 0.5 % | 0.3 w/m2-sr |
| Stability Requirements |  | < 0.14%/yr |  | < 0.1%/yr |  |
| Climate
Stability Goals |  | < 0.6 w/m2/dec
< 0.03 %/yr |  | < 0.2 w/m2/dec
< 0.02%/yr |  |

**Radiometric Performance Requirements**

**5-Year CERES Mission Lifetime**

## CERES Terra/Aqua Health & Status

**With the exception of the SW channel on the CERES/Aqua FM-4 Instrument,**
**the CERES Terra/Aqua instruments are functioning nominally...**

| Spacecraft | Instruments | Launch | Science Initiation | Collected Data
(Months) |
| --- | --- | --- | --- | --- |
| TRMM | PFM | 11/97 | 1/98 | 9 |
| Terra | FM1, FM2 | 12/99 | 3/00 | 85 + |
| Aqua | FM3, FM4 | 5/02 | 6/02 | 58 + |
| NPP | FM5 | 2009 | ? | - |

**24 + Instrument Years of Data**

## Cal-Val Approach

**Pre-Launch **
**Implement a rigorous & thorough ground calibration/characterization program**
**Cal/Val role must be prominent in original proposal and SOW**
**System level characterization is typically last test performed prior to delivery of the instrument**
**Cost and schedule constraints typically drive programs at that point**
**Post-Launch**
**Implement a protocol of independent studies to characterize on-orbit performance**
**Studies should cover all spectral, spatial and temporal scales as well as data product levels**
**Continuous development of new validation studies**
**Data Product Release Strategy**
**Develop a logical and well understood approach to data release.**
**Minimize the number of Editions/Versions of Data**
**Utilize Data Quality Summaries for the community**

## Radiometric Calibration Facility

- Narrow Field of View Blackbody (NFBB) is primary standard (Emissivity of greater than 0.9999)
- 12.5 cm Wide Field of View Blackbody (WFBB)
- Cold Space Reference (CSR) blackbodies
- New SW reference source (SWRS) with minimum LW variations and better spectral characterization
- 5 cm i.d. integrating sphere with associated optics
- Cryogenically cooled Transfer Active Cavity Radiometer (TACR)
- Point Response Function characterization source
- Constant Radiance Reference to determine scan dependent offsets
- Earth infrared radiation simulators
- Liquid nitrogen cooled shroud wall

## CERES Instrument Radiometric Validation Activities

|  |  | Product | Spatial
Scale | Temporal 
Scale | Metric | Spectral
Band |
| --- | --- | --- | --- | --- | --- | --- |
|  | Internal BB | Filtered
Radiance | N/A | N/A | Absolute Stability | TOT, WN |
| On-Board | Internal Lamp | Filtered
Radiance | N/A | N/A | Absolute Stability | SW |
|  | Solar | Filtered
Radiance | N/A | N/A | Relative Stability | TOT, SW |
|  | Theoretical Line-by-Line | Filtered
Radiance | > 20 Km | Instantaneous | Inter-Channel
Theoretical Agreement | TOT, WN |
|  | Unfiltering Algorithm Theoretical Validation | N/A | N/A | N/A | N/A | TOT, SW, WN |
|  | Inter-satellite 
(Direct Comparison) | Unfiltered Radiance | 1-deg Grid | 1 per crossing | Inter-Instrument Agreement, Stability | TOT, SW, WN |
| Vicarious | Globally Matched Pixels
(Direct Comparison) | Unfiltered Radiance | Pixel to Pixel | Daily | Inter-Instrument Agreement | TOT, SW, WN |
|  | Tropical Mean
(Geographical Average) | Unfiltered Radiance | 20N – 20S | Monthly | Inter-Channel Agreement, Stability | TOT, WN |
|  | DCC Albedo | Unfiltered Radiance | >40 Km | Monthly | Inter-Instrument agreement, Stability | SW |
|  | DCC 3-channel | Unfiltered Radiance | >100 Km | Monthly | Inter-Channel consistency, stability | TOT, SW |
|  | TIme Space Averaging | Fluxes | Global | Monthly | Inter-Instrument Agreement | LW, SW |
|  | Lunar Radiance Measurements | Filtered Radiance | Sub Pixel | Quarterly | Inter-Instrument Agreement | LW, SW, WN |

**CERES Instrument Radiometric Validation Activities**

## BDS and ERBE-Like Data Product Release Strategy

**Edition1_CV - Static Algorithms and coefficients - baseline product used in ****	****	****             cal/val protocol**
**Edition2 - Utilizes temporally varying coefficients to correct for traceable ****	****	****       radiometric drift. All spectral changes are broadband and ‘gray’.**
**Edition3 - **_***Release date Fall 2007***_**.  Will incorporate temporally varying           **
**                 ****spectral artifacts in the SW measurements. A complete re-analysis**
**                 ****of Ground Calibration with additional component  characterization**
**                 ****measurements.**
**User Applied Revisions - Advance capabilities to the users prior to the **
**	****	****	****	****	****release of the next Edition.**
**Edition2 products lag Edition1 by a minimum of 4 months**

## CERES Unfiltered Radiance Summary

-            Units are in %/yr

|  | Edition1_CV |  |  |  | Edition2 |  |  |  | Edition2_Rev1 |  |  |  | Edition 3 |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | FM1 | FM2 | FM3 | FM4 | FM1 | FM2 | FM3 | FM4 | FM1 | FM2 | FM3 | FM4 | FM1 | FM2 | FM3 | FM4 |
| LWday | .3 | .6 | .4 | .4 | .125 | .125 | .3 | .3 | .125 | .125 | .15 | .15 | <.1 | <.1 | <.1 | <.1 |
| LWnight | .1 | .125 | .125 | .125 | <.1 | <.1 | .1 | .1 | <.1 | <.1 | .1 | .1 | <.1 | <.1 | <.1 | <.1 |
| SW | .2 | .4 | .4 | .5 | .2 | .3 | .3 | .4 | <.1 | <.1 | .25 | .25 | <.1 | <.1 | <.1 | <.1 |
| WN | <.1 | <.1 | .1 | .1 | <.1 | <.1 | .1 | .1 | <.1 | <.1 | .1 | .1 | <.1 | <.1 | <.1 | <.1 |

**(Anticipated)**

**Cal/Val Protocol demonstrates radiometric stability of the data ****	****	****products through 12/2006 of.... **

**CERES Unfiltered Radiance Summary**

## Lessons Learned / Future Direction

**How do we move CERES towards achieving the new climate calibration stability goals?**
**In the future there will only be a single CERES or CERES II instrument per spacecraft, eliminating key Direct Comparison validation capabilities...**
_**New Programmatic Paradigms**_** **
**	**- Maintain positive/open relationship with hardware provider. Avoid ‘Us’ vs. ‘Them’ mentality.
_**Handling Procedures**_** **
**	**- Keep instruments clean, develop inspection/cleaning procedures.
_**Ground Characterization Procedures**_** **
**	**- Improve absolute traceability, Collaborate with NIST, other international agencies
_**Operational Mode**_** **
**	**- Do not point optics in ‘forward’ looking direction
_**Hardware Improvements**_** **
**	**- Improve post-launch spectral characterization capabilities