# Presentation: 762283

## Hyperspectral Data Compression Workshop

**May 23, 2003**

**Hyperspectral Data Compression Workshop**

**Spectral Considerations for the Measurement of Carbon**

**Janette C. Gervin, **
**Robert G. Knox, Elizabeth M. Middleton, **
**Antonio Mannino, Watson W. Gregg,**
**Charles R. McClain, Forrest G. Hall, and Jaime Esper**
**NASA Goddard Space Flight Center**
**Greenbelt, MD  20771**

## Greenhouse Gases and Warming

-  Weather station records and ship-based observations indicate that global mean surface air temperature warmed between about 0.4 and 0.8 o C (0.7 and 1.5 o F) during the 20th century.

-   A major contributor to climate warming is the steady increase in atmospheric greenhouse gases.

## Uncertain Futures

**Uncertain Futures**

- As CO2 emissions have increased, the land and oceans have absorbed more and more carbon.
- Projections of future CO2 levels depend on our knowledge of the biosphere and how it interacts with climate
- Given identical human emissions, different models project dramatically different futures.
***Which is correct?  How can we know?***

## GCCP Technology Activities Roadmap

**GCCP Technology Activities Roadmap**

## Project Description: Global Carbon Cycle Plan

**Mission Objective: **multi-year mission to determine the Geographic Distribution and the Seasonal and Interannual Variation of Global Carbon Exchange between the Earth’s Atmosphere, its Land Masses and Oceans; to determine the Effect of Climate Variation and Secular Trends on the Geographic and Temporal Dynamics of the Global Carbon Cycle; and to provide Information Supportive of Policy Decisions and Mitigation Approaches
**Organizations:  **Lead: Goddard Space Flight Center designated lead by HQ  Partners:  Other NASA Centers, other federal agencies, and university scientists
**Mission Description:  **Five to seven missions in (primarily) sun-synchronous orbits measure atmospheric carbon dioxide, aerosols, ocean and coastal carbon productivity, and low and high density land biomass.
**Launch:  **To be launched on two-year centers starting in 2008
- Pathfinder CO2    Ocean Carbon    Low Density Biomass High Density Biomass Advanced CO2

## Assumed Measurement Requirements (2001)

- Note:  Sun synchronous (unless otherwise stated), low earth orbits, and mission duration of at least 3 years (technology permitting), assumed.

**Assumed Measurement Requirements (2001)**

## Nominal Set of GCCP Missions

- Description: A small satellite mission that makes high-precision (1 to 2 ppmv) global measurements of atmospheric column CO2 abundance

- Description: A small satellite mission that makes those ocean color measurements critical to the determination of ocean biomass, primary  productivity, and dissolved organic matter

- Pathfinder CO2

- Ocean Carbon

- Low Density Biomass
- Coastal Ocean

- Description: A satellite mission that provides a synoptic view of the Earth’s ecosystems, their spatial distribution, and temporal dynamics with global measurements of land cover, land cover change, and ocean surface chlorophyll

- High Density Biomass

- Description: A small satellite mission that measures the global concentration of carbon dioxide and oxygen in the lower troposphere

- Advanced CO2

- Description: A satellite mission that provides improved regional and global estimates of vegetation biomass and carbon stocks, studies the response of  terrestrial ecosystems to major disturbances, and measures the rate of recovery

- Instruments: A pulsed, dual frequency, tunable laser sounder operating in the 1570 nm band for carbon dioxide detection and in the 770 nm band for oxygen detection, coupled with a lightweight passive spectrometer for measuring absorption of reflected sunlight* in the same spectral regions

- Instruments: A P-band SAR operating at 0.44 GHz and a multi-track, 1.064 micron, imaging laser altimeter with a capability of resolving 0.5 m differences in vegetation height

- Instrument: A hyperspectral imager providing high signal-to-noise ratios and covering a frequency range from 450 to 2350 nm with a SWIR bandwidth of 10 nm and a VNIR  bandwidth of 5 nm

- Instrument: A scanning telescope equipped with an on-board solar calibrator that makes irradiance measurements in 10 spectral bands from the ultraviolet to the near infrared; additional bands or complementary hyper-spectral instrument to obtain coastal ocean data

-  Instrument: A passive spectrometer with a 10 km spatial resolution that provides high signal-to-noise ratio detection of atmospheric CO2 and O2 during the day time portion of the orbit

- Mission Life: 3-5 years
- Orbit: Sun synchronous,
- 705 km for passive inst.,
-  400-590 km for lidars
- Spacecraft: Small, low-
- cost, three-axis stabilized,
- nadir pointing

## Ocean Carbon

**Ocean Carbon**

- Description: A small satellite mission that makes those ocean color measurements critical to the determination of ocean biomass, primary  productivity, and dissolved organic matter
- Instrument: A rotating, scanning telescope equipped with an on-board solar calibrator that makes irradiance measurements in 10 spectral bands from the ultraviolet to the near infrared; additional bands or complementary hyperspectral instrument to obtain coastal ocean data
- Spacecraft: A small, low-cost, three-axis stabilized, nadir pointing spacecraft from the RSDO catalog with a propulsion system for orbit raising, maintenance, and maneuvers

**Key Technologies: **selection of bands not generally used in land applications, improvements in sensor design, and the use of onboard data processing to optimize data retrieval

**Launch Date: **FY 2010
**Mission Life:** 5 Years
**Orbit: **705 km polar, sun-synchronous, with a 12:00 noon crossing time** **
**Space Access: **Pegasus XL or equivalent class launch vehicle
**Mission Options:** A single instrument mission

## Low Density Biomass/Coastal Ocean

**Launch Date:** FY 2012
**Mission Life:**5 Years
**Orbit:**  705 km circular sun-synchronous with a 10:30 a.m. descending node
**Space Access:** Taurus or equivalent class launch vehicle

**Key Technologies:**  Large area focal plane arrays, large capacity on-board recorders, and high rate downlink systems for improved mission performance

**Low Density Biomass/Coastal Ocean**

- Description: A satellite mission that provides a synoptic view of the Earth’s ecosystems, their spatial distribution, and temporal dynamics with global measurements of land cover, land cover change, and ocean surface chlorophyll
- Instrument: A hyperspectral imager providing high signal-to-noise ratios and covering a frequency range from 450 to 2350 nm with a SWIR bandwidth of 10 nm and a VNIR  bandwidth of 5 nm
- Spacecraft: A low-cost, three-axis stabilized, nadir pointing spacecraft from the RSDO catalog with a propulsion system sized to allow formation flying with other land imaging platforms

## Coastal Ocean Bands

**Coastal Ocean Bands**

*Coastal Ocean*
- band 	width
- center	(nm)
- 360	10
- 380	10
- 412	10
- 443	10
- 490	10
- 510	10
- 555	10
- 660	10
- 670	10
- 680	10

## Low Density Biomass Bands

-  Band positions plotted over 6S modeled nadir reflectance from a vegetated pixel, using a US standard atmosphere (1962) and continental-type aerosols. Top-of-atmosphere reflectance: **direct beam** is the signal from the land-surface pixel - attenuated by absorption and scattering, **total** includes path radiance from molecular scattering and aerosols.

*Terrestrial Biomass*
- band 	width
- center	(nm)
- 531	6
- 570	3
- 665	10
- 680	5
- 697.5	2
- 750	5
- 780	10

**Low Density Biomass Bands**

## Atmospheric Transmission

- .Atmospheric transmission after 2-way gaseous line absorption by H2O and O2, calculated from the HITRAN 2000 database, using the GENSPECT Matlab toolbox. (Water vapor mixing ratios from 1976 U.S. standard atmosphere.) UV and visible wavelengths are also attenuated by broad ozone features (not shown).

**Atmospheric Transmission**

## “A Fork in the Road”

- Narrow Bands in atmospheric windows, with broadband
- 	aerosol/atmospheric correction
- (e.g., MODIS surface reflectance products)
- Hyperspectral with enough fidelity to _both_
- -do atmospheric correction and
- -resolve vegetation spectral features
- 	(e.g., derivative spectra)

## Ongoing GSFC Study of a Combined GEO Hyperspectral Mission

**Address the original science requirements, while increasing the scientific return of a single spacecraft**
**Renewed interest in advanced measurement capabilities from geostationary altitudes, particularly hyperspectral measurements. **
**New emphasis on light-use efficiency and ecosystem carbon exchange**
**Full diurnal coverage, hemispheric or near-global**
**Single spacecraft, near geostationary, or LEO constellation **

## Instrument Performance

**1.2-meter aperture required for 100-meter resolution diffraction limited performance.**
**340nm to 1000nm, and 1000nm to 2400nm grating spectrometers.**
**Silicon CCDs or Photodiode arrays used for the visible and near Infrared channels, and Mercury Cadmium Telluride detectors used for the Short Wave Infrared Channels. **
**Scan perpendicular to the spatial direction, and parallel to the spectral direction on the detector.**
**Size ~ 1.3 x 1.3  x 2.5 meters, mass ~ 1000 Kg, with adequate contingency. Power ~ 350 watts, including thermal control.  **

## SNR Performance

-  Effective resolution constrained by SNR requirements: 1000:1
-  A 4-degree per minute scan rate results in one full Earth-scan every 3 hrs

## Conclusions

**Preliminary study demonstrates both advantages and challenges of a GEO hyperspectral platform.**
**Advantages are full diurnal hemispheric coverage of the Earth, or near-global coverage at a minimum rate of once every two days, all achievable with a single spacecraft.**
**The challenge still remains to obtain desired high spatial and spectral resolution hyperspectral images with high SNR .**
**EO-1:  technology pathfinder**
**EO-1 Hyperion data valuable for requirements studies and testing algorithms**