Status Report

NASA Request for Information: Ocean Color Remote Sensing Vicarious in situ Calibration Instruments

By SpaceRef Editor
January 4, 2013
Filed under , , ,

Synopsis – Jan 04, 2013

General Information

Solicitation Number: NNH13ZDA005L
Posted Date: Jan 04, 2013
FedBizOpps Posted Date: Jan 04, 2013
Recovery and Reinvestment Act Action: No
Original Response Date: Feb 15, 2013
Current Response Date: Feb 15, 2013
Classification Code: A — Research and Development
NAICS Code: 541712

Contracting Office Address

NASA/Goddard Space Flight Center, NASA Headquarters Acquisition Branch, Code 210.H, Greenbelt, MD 20771



A. Request Summary

The National Aeronautics and Space Administration (NASA) is seeking ways to provide or develop in situ vicarious calibration instruments, systems, and approaches for a future mission’s ocean color instrument. This RFI asks organizations to provide information regarding current instrument capabilities or descriptions of developments that would be needed in order to provide an in situ vicarious calibration capability for maintaining global climate quality ocean color remote sensing reflectances for a multi- or hyperspectral sensor. “Vicarious” calibration for ocean color refers to a final bias adjustment to the calibrated, spectral top-of-atmosphere radiances observed by an ocean color instrument. Responses could consider the PACE Science Definition Team (SDT) report (found at ) for details of sample vicarious calibration for ocean color requirements, particularly the details in Section 4.6.1 of the report.

B. Background

Earth’s ocean supports a nearly one trillion-dollar economy. There is increasing climate variability and change occurring in the Earth System which impacts aquatic ecology, chemistry, and biology. Satellite ocean color data provides new information for understanding Earth’s living ocean and for improving forecasts of Earth System variability and the impacts and feedbacks on ocean ecosystems and biogeochemistry (e.g., fisheries, carbon cycle, harmful algal blooms and public health, marine resources, land/ocean interactions, etc.). A satellite ocean color mission can achieve these objectives by making climate quality global ocean color measurements that are essential for understanding aspects of the Earth system, such as the carbon cycle and its interrelationship with climate change, and by expanding our understanding about ocean ecology and biogeochemistry. The success of an ocean color mission relies on a combination of satellite remote sensing, field measurements (e.g., ship, mooring, and drifter), Earth system modeling, and synthesis efforts designed to address specific science questions.

The ability of an ocean color mission to meet its key science objectives depends primarily upon the quality, accuracy, and precision of the ocean ecosystem, aerosol, and cloud data products that can be derived from engineering data collected by the sensor. To produce a time series of spectral ocean color data of sufficient quality for research, the ocean color sensor must have stringent calibration and validation (cal/val) data requirements for quantifying ocean color sensor performance; the accuracy, precision, and associated uncertainties of the retrievals; and their drift over the spacecraft operational lifetime. Future NASA ocean color science applications require highly accurate Rrs(Lambda) (spectral remote sensing reflectances). Maintaining sufficient accuracy over the lifetime of the mission will require a robust vicarious calibration program that complements the onboard calibration devices and enables routine verification of the ocean color instrument calibration while operating on orbit. In situ measurements of Rrs(Lambda) will provide the principle source of ground truth for the operational vicarious calibration activity.

Historically for ocean color retrievals, measured top of the atmosphere (TOA) reflectances are regressed against coincident near-surface ocean reflectances to establish a gain factor for a given satellite ocean radiometer. This process is referred to as the ‘vicarious calibration’ and, for heritage ocean missions, as well as for current and future missions, it requires a dedicated calibration program.

Vicarious calibration measurements are best conducted at an open ocean location where atmospheric aerosol loads and variability are minimal (e.g., most heritage sensors relied on measurements made off Lana’i Hawaii by the Marine Optical BuoY). For any given satellite-surface reflectance pair, some uncertainty remains due to unconstrained aerosol impacts. However, collecting many paired observations over all seasons minimizes this uncertainty, such that the time series of observations converges on a single gain factor. For the SeaWiFS mission, this convergence required more than two years. Once a reliable gain factor is established (one goal would be to achieve this gain within the first year of operations), it is used to scale TOA reflectances measured elsewhere. This vicarious calibration procedure is not impacted by global variability in atmospheric aerosols, although some error can still exist if an aerosol bias persists in all the field-satellite data pairs. Historically, atmospheric measurements have not accompanied the ocean vicarious calibration measurements. Inclusion of additional observations (e.g., sun-photometer measurements) would be advised.

Once a sensor gain factor is determined, the resultant calibrated global data set of TOA reflectances must then be corrected for local atmospheric conditions to retrieve water-leaving radiances, and it is in this procedure (currently based on the NIR and SWIR approach described above) that errors can arise from uncertainties in aerosol characteristics. In addition to the magnitude of the aerosol optical depth (AOD) itself, spectral AOD and absorbing AOD (AAOD) ‘slopes’ of different aerosol types need to be taken into account for maximum aerosol correction accuracy. Key aerosol types that dominate at different locations and in different seasons over the ocean include Saharan dust, Gobi dust, different types of organic (“brown”) carbon (e.g., most wildfire smoke and urban pollution particles), black carbon (e.g. from diesel and some fire combustion products), sea salt, and sulfate particles.

The shortest measurement band in most heritage ocean color missions (e.g., SeaWiFS, MODIS and MERIS) has been near 410 nm. As noted above, uncertainties in atmospheric corrections increase with decreasing wavelength, and at 410 nm, errors due to uncertainties in aerosol amount, type, and vertical distribution can be significant. For future ocean color missions, ocean retrievals could be extended into the near-ultraviolet (NUV) down to 350 nm. This extension may necessitate a reevaluation of the atmospheric correction approach due to difference in atmospheric optical properties between the UV and visible wavelengths (specifically, increased contribution from absorbing aerosols, as well as impacts of scattering aerosols). An evaluation is also needed of uncertainties associated with atmospheric pressure effects on the gas-scattering contribution to the TOA signal. Retrieval of ocean color dissolved organic material (CDOM) may be a particularly challenging issue for some regions and times. Specifically, the spectral shape of absorption by some aerosol types is similar to that of oceanic CDOM, both of which are most strongly absorbing in the UV. Inaccurate separation of these different components can result in significant biases in CDOM retrievals (particularly, for example, in coastal regions with high CDOM and low suspended sediment concentration), although the extent of this issue has not yet been quantified.

Sufficiently robust in situ calibration/validation systems need to be developed for a future ocean color mission. Therefore, NASA is requesting information from the community on capabilities and new approaches that are available for providing in situ instrumentation to support ocean color vicarious calibration requirements. Calibration requirements for the ocean color instrument are suggested to be a prelaunch absolute calibration of 2% and on-orbit absolute calibration accuracy (before vicarious calibration) of better than 5%. Vicarious calibration should include ground-based remote sensing reflectance (Rrs) data for evaluating postlaunch instrument gains. The recommended in situ vicarious calibration instrument(s) systems to support ocean color science applications might include the following features:

1. Spectral range from 350-900 nm at less than or equal to 3 nm resolution 2. Total spectral accuracies less than or equal to 5% including contributions from all instrument calibrations and data processing steps (with NIST traceability) 3. Temporal spectral stability less than or equal to 1% per deployment (with NIST traceability) 4. Sufficient data acquisition rates to reduce vicarious gain standard errors to less than or equal to 0.2% within one year of launch (post-launch, implying the need for multiple systems that are simultaneously deployed) 5. Capability of autonomous operation for some application.

Additionally, it would be expected that complementary routine field campaigns would also support a future mission to verify data quality and evaluate data product uncertainties and for data product validation. Such fieldwork is not the subject of this RFI.

C. Requested Information:

Responses to this RFI will be in the form of a PDF document that is uploaded through NASA’s NSPIRES system (see Instructions below).

Respondents are asked to provide information about existing capabilities and/or capabilities that need to be developed which could meet the requirements described above. Each response to the RFI should address the following topics, in this order:

a. A description of the existing capabilities and/or capabilities that need to be developed and how those capabilities would meet all of the desired vicarious calibration instrument(s) requirement(s).

b. A justification for why this particular capability or approach would meet the requirement(s).

c. An estimated total cost and schedule with any key details driving the cost. The schedule should indicate the length of the period for development.

D. Additional Information

NASA intends to use the results of this RFI for informational purposes only. This RFI does not constitute a Request for Proposal, and it is not to be construed as a commitment by the Government to enter into a contract, nor will the Government pay for the information submitted in response to this request. At NASA’s discretion, we may contact respondents to further discuss their RFI input. Responses should include the following information:

Company name, address, point of contact, phone number, fax, E-mail, and website (if applicable), description of the type of business, number of years in business, and affiliate information, including parent company and/or joint venture partners if applicable.

All proprietary information received in response to this RFI should be marked “proprietary” by the submitter and it will be handled and protected accordingly by NASA. To the extent necessary, NASA may provide proprietary information to its support service contractors who are under an obligation to keep third-party proprietary information in confidence. By submitting a response to this RFI, the responder is deemed to have consented to the use of proprietary information for internal NASA purposes and release of any such proprietary information to such NASA support service contractors. Responses to the RFI will not be returned.

All responses submitted in response to this RFI must be submitted in electronic form via NSPIRES, the NASA online announcement data management system, located at . For this RFI, a response submission will take the form of a Notice of Intent (NOI) within the NSPIRES online announcement data management system. The RFI response itself will be a PDF-formatted document that is attached (uploaded) to the NSPIRES system.

Page Limitation: The response must be limited to 5 pages. A page is defined as one (1) sheet 8.5 x 11 inches with one-inch margins using a minimum of 12-point font size for text and 8-point for graphs.

You must be registered with NSPIRES to submit a RFI response. Registration instructions can be found at select “Getting an account”). Neither institution registration nor an institution affiliation is required to respond to this RFI.

1. Log in to your account at . 2. Select “Proposals” from your account page. 3. Select “Create NOI” from your proposals page. 4. Click “Continue” on the next page. 5. Select “Request for Information: TBD (Ocean Color Remote Sensing Vicarious (In Situ) Calibration Instrument(s))” from the bullet list of announcements. Click “Continue”. 6. Enter RFI response title (“NOI title” field will be shown). 7. Select “do not link at this time” for submitting organization page. 8. Click “Save” on next page. 9. It is not necessary to complete any of the “NOI Details”; all requested information must be included in the attached PDF document. Information, which is entered into “NOI Details” but not included in the attached PDF document, will not be considered. 10. Prepare your RFI response offline and save as a PDF document (note NSPIRES instructions on .pdf formats). The response document must include the respondent’s Name, institution, phone number, and E-mail address so the file is self-contained. File names format should be “Respondent Last Name – First Name – RFI”. The response should not exceed four pages in length. 11. To attach (upload) your PDF document: a. Click “add” under NOI attachments section; b. Select “Proposal Document” from the drop down list; c. Browse to attach your PDF file; d. Select “Upload”; e. Click “OK”; f. Your RFI document has been uploaded to NSPIRES. 12. Click “Submit NOI” button. NOTE that this does not complete the submission process. 13. Ignore any warnings about incomplete NOI elements. Ensure that your NOI document is attached and click “Continue”. 14. Click “Submit”. This will take you to the NOI submission confirmation page, which provides you with the NOI/RFI number for your records.

Please note: You may delete and replace form fields and uploaded documents anytime before the submission deadline. Submitted NOIs cannot be deleted.

Point of Contact

Name: Mr. Parminder Ghuman
Title: Instrument Incubator Program Manager
Phone: 301-286-8001
Fax: 301-286-0321

SpaceRef staff editor.