# Presentation: 051919

## CERES Instrument: Reality vs. Star Trek

**Kory J. Priestley & Robert B. Lee III**
**CERES Instrument Working Group Leaders**

## Slide 2

## Components of the Earth’s Radiative Energy Budget

## 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
- Channel fields of view overlap by <98%
- On-board calibration capability

## Slide 5

## Aqua Spacecraft

## EOS -AQUA 

*EOS -AQUA *

- 02:54:58 PDT
- May 04, 2002
- Vandenberg AFB

## Slide 8

## Single Orbit of CERES Aqua Data

**Single Orbit of CERES Aqua Data**
**(Polar Orbit, Rotating Azimuth Mode)**

## Aqua First Light Images

**Aqua First Light Images**
**June 22, 2002**

## Remote Sensing Experiment Lifecycle

## 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
- Channel fields of view overlap by <98%
- On-board calibration capability

## 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
- Channel fields of view overlap by <98%
- On-board calibration capability

## CERES Sensor

## CERES Sensor

## CERES Sensor

## CERES Sensor

## CERES Sensor

## CERES Sensor

## CERES Sensor

## Detail of a CERES Flight Detector

**Detail of a CERES Flight Detector**

- Can sense temperature changes at the micro-Kelvin level....

## CERES Detector Bridge Amplifier Circuit

**CERES Detector Bridge Amplifier Circuit**

## 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
- Channel fields of view overlap by <98%
- On-board calibration capability

## Surface Scan Patterns

## Surface Scan Patterns

**WHY FAPS & RAPS?**

## Surface Scan Patterns

**WHY FAPS & RAPS?**
**Answer: Angular Models**

## What the heck is an Angular Model???

## What the heck is an Angular Model???

- For a single footprint, the CERES sensors only measure the amount of energy leaving the top of the atmosphere in a given direction....

## What the heck is an Angular Model???

- For a single footprint, the CERES sensors only measure the amount of energy leaving the top of the atmosphere in a given direction....
- What we need to know is the TOTAL energy leaving the atmosphere in all directions for a single footprint......

## What the heck is an Angular Model???

- For a single footprint, the CERES sensors only measure the amount of energy leaving the top of the atmosphere in a given direction....
- What we need to know is the TOTAL energy leaving the atmosphere in all directions for a single footprint......
- Angular Models, R, convert, or scale, a directional quantity (what we measure) to a hemispherical quantity (what we need)!

## Thought Experiment... Light Bulb!!

## Thought Experiment... Light Bulb!!

## Light Scatter Activity.....

## So, Why RAPS and FAPS.....

- FAPS instrument provides uniform spatial coverage for optimal Earth Radiation Data Products....
- RAPS instrument data is used to develop Angular Models....

## 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
- Channel fields of view overlap by <98%
- On-board calibration capability

## Why is Calibration Accuracy Important?

**Accurate and useful monitoring of the Global climate requires instruments that very accurately measure small perturbations about a relatively large mean value.**
- An instantaneous doubling of atmospheric CO2 would produce a temporary change in TOA flux of ~4 W/m2. (~4 to 8 counts)
- Apparent change in Earth emitted radiation from ERBE to CERES of ~4W/m2 on decadal scale (Science, Feb 02, 2002).
- Both of these events represent a change in the mean signal of ~ 2%.
- To adequately measure these events a signal-to-noise ratio of at least 2:1 is required, leading to absolute accuracy requirements at the sub 1% level.
**The CERES instruments are the most highly calibrated and characterized Earth Radiation Budget instruments to have ever flown...**

## Components of the Earth’s Radiative Energy Budget

## Why is Calibration Accuracy Important?

**Accurate and useful monitoring of the Global climate requires instruments that very accurately measure small perturbations about a relatively large mean value.**
- An instantaneous doubling of atmospheric CO2 would produce a temporary change in TOA flux of ~4 W/m2. (~4 to 8 counts)
- Apparent change in Earth emitted radiation from ERBE to CERES of ~4W/m2 on decadal scale (Science, Feb 02, 2002).
- Both of these events represent a change in the mean signal of ~ 2%.
- To adequately measure these events a signal-to-noise ratio of at least 2:1 is required, leading to absolute accuracy requirements at the sub 1% level.
**The CERES instruments are the most highly calibrated and characterized Earth Radiation Budget instruments to have ever flown...**

## CERES On-orbit Calibration Philosophy

**Supplemental**
**Validation**
**Studies**

## CERES Onboard Calibration Sources

_**Internal Calibration Module (ICM)**_
- Blackbodies for the Total and Window channels
- Temperature knowledge obtained via Platinum Resistance Thermometers (PRTs)
- Quartz-halogen tungsten lamp for the Shortwave channel
- ICM Provides 3 unique radiance levels for the SW and LW sources

## CERES Solar Calibration

_**Mirror Attenuator Mosaic **_
- The MAM is a Solar Diffuser plate which attenuates direct solar view
- Fabricated from a Nickel substrate with Aluminum coated spherical cavities or divots
- Forward baffles limit Field-of-View to ± 4-degrees, prohibiting stray light contamination
- Provides a Relative calibration of the Shortwave channel and the SW portion of the Total channel

## 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

## Role of Clouds and Aerosols on the Radiation Budget

**Role of Clouds and Aerosols on the Radiation Budget**

## 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 | Tropical 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 |

**CERES Instrument Radiometric Validation Activities**

## Slide 45

## Slide 46

## Slide 47

## Earth as a Heat Engine

**Earth as a Heat Engine**

## CERES Proto Flight Model

**CERES Proto Flight Model**
**Edition 2 End-to-End Spectral Response**

## Instrument Working Group

**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 and engineering**

## Slide 51

## Slide 52

## Information Flow: Earth Scene to Level 0 Data

**Information Flow: Earth Scene to Level 0 Data**

## Instrument Optical Response Function

**Instrument Optical Response Function**

## Design Challenges

**Thermal Control**
**Pointing Knowledge**
**Motors and Bearings**
**Detector Fabrication**
**Data Production and Analysis**

## Instrument Point Response Function

**Instrument Point Response Function**

## Thought Experiment... Light Bulb!!