# Presentation: 880903

## Next-Generation OSVW Instrument Studies at JPL

**Ernesto Rodr****íguez**
**Jet Propulsion Laboratory**
**California Institute of Technology**
**November 30, 2007**

**Notes:**
Note that JPL has been asked by NOAA to conduct a study of 3 scenarios for future ocean surface vector winds missions to meet NOAA’s emerging needs.

## QuikSCAT Replacement Concept

**Measurement Objectives**: 12.5 km resolution winds in the 3-30m/s range (limited by rain contamination as in QuikSCAT).
**Instrument Concept:** Ku-band real aperture scatterometer, with instrument design to be an evolutionary pathway to XOVWM
**Foreseen Impact on NOAA Operations:**
- Continues the QuikSCAT data stream
- Maximum wind speed limits hurricane coverage up to category 1
- Performance in hurricanes is limited by rain contamination
- Measurements within 20 km of the coast are corrupted by strong signal reflections from land

**Notes:**
First of the options that NOAA has asked JPL to examine as part of the study to be completed in January 2008. Remark that a build to print copy of QuikSCAT is impossible due to parts obsolescence or unavailability: QuikSCAT was designed with late 80’s technology.

## XOVWM Concept

**Measurement Objectives**: 5 km resolution winds in the 2 m/s to 80m/s range and in rain.
**Instrument Concept:** Ku-band synthetic aperture radar (SAR) and C-band real aperture radar (RAR) scatterometers, X-band radiometer.
**Foreseen Impact on NOAA Operations:**
- Order of magnitude improvement in tropical cyclone monitoring:
- full wind speed range (to category 5), resolution of the eye and rain bands, improvements to hurricane models and prediction
- •	Coastal coverage to 5 km of land (2.5 km goal)
- •	Significantly better forecasting of extra-tropical cyclones (higher resolution and higher wind speeds)
- High resolution winds are required for optimal results from next generation NWP models

**Notes:**
Second of the options that NOAA has asked JPL to examine as part of the study to be completed in January 2008. This option is designed to address the requirements in the NOAA 2006 OSVW report, which are part of the NOAA CORL. It is also designed to meet the requirements of the NRC Decadal Review recommended XOVWM (Extended Ocean Vector Winds Mission) mission.

## XOVWM Constellation Concept 

**Measurement Objectives**: as in XOVWM option, but improving temporal coverage by about a factor of 2
**Instrument Concept:** 2 XOVWM satellites in orbits that are configured to improve temporal revisit
**Foreseen Impact on NOAA Operations:**
- Improved monitoring of fast moving tropical and extra-tropical cyclones
- Resolves the diurnal cycle of winds
- Operational redundancy
- Cost savings will depend on funding and acquisition strategy

**Notes:**
The 3rd option: the desirable long term option for *operational* OSVW measurements. It has the advantage of lower long-term cost and better temporal revisit performance: 1 XOVWM- twice per day. 2 XOVWM- 4 times per day.

## XOVWM Design Philosophy

- Measurement goals and priorities provided by NOAA OSVW Study (Chang & Jelenak, 2006)
- All weather capability (clouds and rain)
- All winds capability (up to category 5 hurricanes)
- High resolution
- Driven by need to resolve hurricane structure, coastal winds, and fronts
- Place high priority on operational needs
- Technology with heritage
- Long mission lifetime
- Long-term vision to include constellations of instruments to provide high temporal sampling into the future
- Be realistic!
- Costs constrained by current budget environment
- Some trades required on the data product characteristics
- Keep it as simple as possible: no NPOESS repeat!

**Notes:**
Mention these were also the requirements of the NRC decadal review XOVWM.

## Target Level 1 Performance Requirements

*For NASA missions, these are ****must meet**** requirements which must be demonstrated prior to launch. NASA instruments frequently perform significantly better the requirements.*

| Parameter | QuikSCAT Replacement | XOVWM |
| --- | --- | --- |
| Operational Life | 5 years with consumables for 10 years | Same |
| Coverage | 90% of the ocean surface in every 24 hour period | Same |
| Maximum Data Loss | 15% | Same |
| Product Latency | < 180 minutes for 85% of the data | Same |
| Wind Vector Cell Resolution | 25/12.5 km | 5 km |
| Coastal Mask | 20 km | 5 km |
| Wind Speed Accuracy | 3-20 m/s: 2 m/s rms | Same |
|  | 20-30 m/s:  10% rms | Same |
|  | 30-80 m/s: not specified | 30-80 m/s:  10 % rms |
| Wind Direction Accuracy | 3-30 m/s: 20 rms | Same |
|  | 30-80 m/s: not specified | 30-80 m/s:  20 rms |

**Notes:**
Stress that these are working requirements, to be reviewed and iterated with the NOAA users. The goal of the work in December is to finalize these top level requirements.

## How Much Effort Has Gone Into Designing XOVWM?

- The XOVWM concept was funded for over a year by NASA
- Concept reviewed and found feasible by independent panel of experts (including NOAA)
- Some issues were identified which required further study
- The NOAA study has addressed the issues identified
- No show-stoppers have been found
- JPL has a team of over 20 people looking at all facets of the design
- Two special studies have been funded address antenna issues: NG Astro and JPL
- Four major aerospace companies (Ball, General Dynamics, Orbital, Lockheed Martin) have studied the spacecraft. All contractors have mature, heritage systems and the capability to deliver the required systems and services
- 3 aerospace companies have looked at the rotation mechanism and found no issues
- UCLA has refined the antenna RF design and is prototyping the antenna feeds
- A grass root cost of XOVWM has been conducted. The QuikSCAT replacement and constellation costs are in process of being completed on schedule. Independent costing by Aerospace Corporation is also in process.

## Designing Next Generation OSVW InstrumentXOVWM 

**QuikSCAT June 1999-**

**Pencil beam scatterometers –** **wider swath**
**Ku-band scatterometers**
**Higher resolution measurements**
**Measurements sensitive to rain**

**Notes:**
Current QuikSCAT instrument has demonstrated *operational* capabilities. SeaWinds instrument also used the same technology and frequency. NSCAT and SeaWinds used the same frequency.

## Model Functions - Ocean Backscatter vs. Wind Speed

- Courtesy D. Esteban Fern_x0005_ández

- Saturation

**Notes:**
Model function relates radar signal sensitivity to wind. Ideally, would like a monotonically increasing curve. For Ku-band, the curve starts saturates after 30 m/s (~60 knots) leading to decreased high wind speed sensitivity and estimation noise. Mention that these functions have multiple decades of measurement heritage. Set ground for QuikSCAT simulation results to be presented by Zorana Jelenak.

## Rain Associated Distortions

**KU band - Attenuation**

**KU band - Rain Backscatter**

**Rain Rate**

***Rain Associated Distortions***

**Ku-band Sigma0**

**Notes:**
In hurricanes, high winds and high rain rates are correlated. The Ku-band radar signal is contaminated by attenuation due to propagation through rain (which obscures the surface wind signal) and scattering from raindrops (which adds signal which is not due to surface winds). At high rain rates and Ku-band frequencies, the contributions from rain are on the same order of magnitude or greater as the wind signature.

## Designing Next Generation OSVW InstrumentXOVWM 

**Pencil beam scatterometers –** **wider swath**
**Ku-band scatterometers**
**Higher resolution measurements**
**Measurements sensitive to rain**
**C-band scatterometers:**
**Less sensitive to rain**
**H-pol wind speed sensitivity **
**doesn’t saturate**
**Lower resolution**

**QuikSCAT June 1999-**

**ASCAT Oct 2006 -**

**IWRAP 2002-**

**Notes:**
Mention also that C-band heritage also includes the ESA ERS scatterometers, which have flown since the 90’s, so the measurement also has extensive experimental heritage. Mention IWRAP measurements have been conducted under the NOAA P3 measurement program.

## Model Functions - Ocean Backscatter vs. Wind Speed

- Courtesy D. Esteban Fern_x0005_ández

- Saturation

- No Saturation

- Data collected by NOAA P3 program using IWRAP (2002-2005)

**Notes:**
Show that at H-pol C-band, there is a strong dependence of the radar signal on wind speed, for *all& wind speeds. Emphasize the important contribution that the IWRAP measurements (NOAA, U. Mass., JPL) have made to made to filling in the data space at high winds.

## Rain Associated Distortions

**KU band - Attenuation**

**C band - Attenuation**

**KU band - Rain Backscatter**

**C band - Rain Backscatter**

**Rain Rate**

***Rain Associated Distortions***

**Ku-band Sigma0**

**Notes:**
Show that for C-band, the rain distortion is significantly smaller than at Ku-band. Hence, C-band is required for high wind speeds and rain.

## Designing Next Generation OSVW InstrumentXOVWM 

**Pencil beam scatterometers –** **wider swath**
**Ku-band scatterometers**
**Higher resolution measurements**
**Measurements sensitive to rain**
**C-band scatterometers:**
**Less sensitive to rain**
**H-pol wind speed sensitivity **
**doesn’t saturate**
**Lower resolution**
**SAR Processing**
**High resolution wind speed measurements**
**Data rate/volume limitations**
**Revisit time/swath limitations**

**QuikSCAT June 1999-**

**ASCAT Oct 2006 -**

**RadarSAT**

**IWRAP 2002-**

**Notes:**
Note that conventional SAR single swath is ~200km. With ScanSAR this can be increased by a factor of ~4. This is still significantly smaller than the XOVWM 1800km swath, which leads to significantly worse temporal sampling, which is key for wind monitoring. Mention that XOVWM uses a simpler SAR processing (unfocused SAR) which, at the cost of reducing spatial resolution from 100’s of meters to ~Order(1km) (still adequate for OSVW), can still have wide-swath km-scale resolution with low data rates, due to onboard data processing.

## SAR Wind Speed Example

- Note NOGAPS model directions and speeds do not agree with SAR data.

- Courtesy of W. Pichel, NOAA, and the JHU/APL SAR winds community)

**Notes:**
High resolution SAR data has enabled the discovery of many very intense wind features near the coasts, where most of the shipping and fishing occurs. SAR’s have not demonstrated operational wind *direction* (only wind speed) measurements. Note that NWP wind model results (colored arrows) completely miss coastal features and forecasts based on these can be significantly off.

## Designing Next Generation OSVW InstrumentXOVWM 

**Pencil beam scatterometers –** **wider swath**
**Ku-band scatterometers**
**Higher resolution measurements**
**Measurements sensitive to rain**
**C-band scatterometers:**
**Less sensitive to rain**
**H-pol wind speed sensitivity **
**doesn’t saturate**
**Lower resolution**
**SAR Processing**
**High resolution wind speed measurements**
**Data rate/volume limitations**
**Revisit time/swath limitations**
**Passive measurements**
**Necessary for rain correction**
**Can help resolve directional ambiguities**
**Wind vector retrievals inferior to scatterometry**

**WindSat Jan 2003-**

**QuikSCAT June 1999-**

**ASCAT Oct 2006 -**

**RadarSAT**

**SeaWinds+AMSR Dec 2002**

**IWRAP 2002-**

**Notes:**
Mention that SeaWinds flew with the Japanese AMSR-E instrument, and they collected Ku-band and passive microwave data simultaneously. Mention that WindSat has significantly increased the understanding of passive measurements of wind and the signature of rain. Mention that XOVWM is not a *scatterometer*, but a true OSVW measurement instrument, which combines active and passive technologies, uniting two communities with extensive knowledge of OSWVW measurements. Mention that the passive is key in determining the rain contamination. Also mention the importance of providing passive imagery measurements, which have a long history of use by the hurricane community (J. Beven, NHC). Mention the inability of passive measurement *by themselves* to provide the OSVW solution due to spatial resolution and rain/cloud contamination. 

## Impact of Passive Channels on Hurricane Wind Speed Rain Correction

- Hurricane Fabian

- Courtesy of R. Milliff & J. Morzel, CoRA

- Wind stress curl

- Results using the latest processing of SeaWinds on Adeos-2 together with AMSR show the improvements which can be obtained by combining active and passive measurements of hurricanes. These results indicate the approach for fulfilling requirements for future ocean vector wind measurement systems.

- Courtesy R. Milliff & J. Morzel

**Notes:**
Show how much better the hurricane structure is defined after making rain corrections from passive measurements, even  for Ku-band scatterometer. Adding C-band to the mix will be even more powerful.

## Designing Next Generation OSVW InstrumentXOVWM 

**Pencil beam scatterometers –** **wider swath**
**Ku-band scatterometers**
**Higher resolution measurements**
**Measurements sensitive to rain**
**C-band scatterometers:**
**Less sensitive to rain**
**H-pol wind speed sensitivity **
**doesn’t saturate**
**Lower resolution**
**SAR Processing**
**High resolution wind speed measurements**
**Data rate/volume limitations**
**Revisit time/swath limitations**
**Passive measurements**
**Necessary for rain correction**
**Can help resolve directional ambiguities**
**Wind vector retrievals inferior to scatterometry**
**Communication Satellites:**
**Large size antenna**
** ****Mature technology**

**WindSat Jan 2003-**

**QuikSCAT June 1999-**

**ASCAT Oct 2006 -**

**RadarSAT**

**SeaWinds+AMSR Dec 2002**

**Communication Satellites - 12m-22m antenna**

**IWRAP 2002-**

**Notes:**
Mention that deployable antennas (used by XOVWM) have become standard in the telecommunication system with ~20 civilian systems deployed or planned for the near future. Telecommunication satellites require proven and reliable technology since the telecommunication industry must rely on the for continuous and long-term operation.

## Designing Next Generation OSVW InstrumentXOVWM 

**Pencil beam scatterometers –** **wider swath**
**Ku-band scatterometers**
**Higher resolution measurements**
**Measurements sensitive to rain**
**C-band scatterometers:**
**Less sensitive to rain**
**H-pol wind speed sensitivity **
**doesn’t saturate**
**Lower resolution**
**SAR Processing**
**High resolution wind speed measurements**
**Data rate/volume limitations**
**Revisit time/swath limitations**
**Passive measurements**
**Necessary for rain correction**
**Can help resolve directional ambiguities**
**Wind vector retrievals inferior to scatterometry**
**Communication Satellites:**
**Large size antenna**
**Mature technology**

**WindSat Jan 2003-**

**QuikSCAT June 1999-**

**ASCAT Oct 2006 -**

**RadarSAT**

**SeaWinds+AMSR Dec 2002**

**E****x****tended ****O****cean ****V****ector ****W****inds ****M****ission - XOVWM**

**IWRAP 2002-**

**Communication Satellites - 12m - 22m antenna**

**Notes:**
Discuss how the XOVWM system incorporates all these proven reliable technological threads to give a quantum jump in measurement performance.

## Extended Ocean Vector Winds Mission (XOVWM) Observatory

**Spin Axis**

**3.5m**

**3.5m**

**46****°**

**40****°**

**Spun instrument**

** ****Ku/C/X  feeds**

**Flat subreflector**

**Deployable mesh reflector antenna**

**Ku/C/X  feeds**

**Spin platform**

-  **XOVWM to provide the next-generation wind measurement capabilities:**
** ****Spatial resolution ~ 5km**
** ****Wind speed range up to Category 5 hurricanes            (155 mph winds)**
** ****All-weather capabilities,    even in rain**
** ****XOVWM builds on proven technologies:**
** ****Ku-band pencil beam (QuikSCAT) and SAR for       high resolution**
**C-band (ASCAT) for high winds and better performance in rain**
** ****Radiometer (AMSR/WindSat) for improved rain correction**

**Notes:**
Emphasize that the symmetry of the deployment implies significantly lower risk for the spinning part. 

## XOVWM Instrument Configuration

***XOVWM Instrument Configuration***

**A feasible thermal concept has been established using only passive components**

**Antenna in stowed package**

**Antenna deploys to 3.5 m by 5 m with back to back mesh reflectors**

**Proven flight heritage deployment mechanism is used**

**Electronics and antenna scan at 20 rpm**

**Total radiator surface area is ~2.4 m****2**** to maintain safe operating temperatures **

**Secondary reflectors simplify deployment**

|  | CBE | CBE + Margin |
| --- | --- | --- |
| Mass | 320 kg | 425 kg |
| Power | 790 W | 950 W |
| Uncompensated Momentum | 300 Nms | 400 Nms |

**Notes:**
Show how antenna can stow compactly to fit in even the smaller launch shrouds. Mention the level of design detail that has enabled to reliable estimation of instrument mass, power, and momentum. Show the level of design detail in all parts of the instrument and mention that significantly more detailed lay-outs exist at JPL.

## QuikSCAT Replacement Instrument Configuration

**Functionally equivalent to QuikSCAT**
**Ku-band instrument**
**12.5 - 25km resolution**
**Severe rain impacts**
**Severe limitations at high wind speeds**

|  | CBE | CBE + Margin |
| --- | --- | --- |
| Mass | 155 kg | 210 kg |
| Power | 190 W | 230 W |
| Uncompensated Momentum | 40 Nms | 55 Nms |

**Notes:**
Mention that the QuikSCAT reflight uses less mass and power than XOVWM, but with measurement limitations, which will be further discussed in Zorana Jelenak’s presentation. JPL will deliver costs for both systems so that NOAA can trade operational utility vs mission cost increase.

## Conclusions

- The XOVWM instrument offers the performance required to satisfy many of the NOAA needs
- The XOVWM builds on existing technology and the engineering design has been significantly matured during the last 2 years
- The concept is feasible
- The concept is implementable with current technology
- We are looking for your feedback on how this instrument could impact your application and look forward to tuning the design to best meet your needs (within cost constraints...)

**Notes:**
Emphasize the need for NOAA user participation and the willingness of JPL to hear their needs and reflect them on the design and simulations to be conducted. Give a brief preview of Zorana’s presentation, which shows the results of the JPL simulation of the XOVWM and QuikSCAT performances.