# Presentation: 789958

## MODIS 

**MODIS **
**Geolocation **
**Status**

- Mash Nishihama
- Raytheon ITSS @NASA Goddard Space Flight Center, Code 922, Greenbelt, MD, USA

- Robert E. Wolfe
- Raytheon ITSS @ NASA Goddard Space Flight Center, Code 922Greenbelt, MD, USA

** ****Geolocation **
**   ****Accuracy**
**      ****Goal**
- MODIS science team has developed remote sensing algorithms to derive global time-series data products on various terrestrial geophysical parameters
- Highly accurate geolocation are required to support MODIS change detection and retrieval of biophysical parameters over heterogeneous land surfaces
*Accuracy Goal is 0.05 *
*of a 1 km Pixel (1****)*

- This work funded under NASA contract NAS5-32373 in the Terrestrial Information Systems Branch (Code 922) at the Goddard Space Flight Center Laboratory for Terrestrial Physics.
*July 13, 2004*

- James A. Kuyper
- SAIC/GSC @NASA Goddard Space Flight Center, Code 922, Greenbelt, MD, USA

**Terra Daily Ground Control Point (GCP) Residuals for C4 (nadir equivalent units)**

**Aqua Daily GCP Residuals (C4)**

**Terra 16-day GCP Residuals (C4)**

**Aqua 16-day GCP Residuals (C4)**

**Terra Summary**

- Excellent results – Collection 4 (C4) Root Mean Square (RMS) error in nadir equivalent units is better than accuracy goal
- Small remaining northern/southern hemisphere difference
- Large errors occur after orbit maneuvers (about 6 per year)
- accuracy in following orbit suspect

**Aqua Summary**

- Good results – C4 RMS error is better than goal in track direction but does not quite meet goal in scan direction (but much better than specification – 150 m)
- Early post-launch coordinate system issue resolved before C4
- Definitive ephemeris is used for best results – causes up to 24 hr processing delay

**Terra Long-Term Trend (LTT)**

- Long-term linear and annual cyclic trend removed in C4
- Original coefficients derived in late 2002 were updated in early 2004 to reflect overall trend (updated coefs. only in forward processing)

**Terra Hemispheric Differences**

- Different trends found in Northern and Southern hemisphere – likely temperature related
- Global trend primarily follows Northern hemisphere because it contains 80% of the GCPs

**Collection 5 Changes Summary**

**Aqua C4 Results**

- Overall scan residuals are 30% larger than Terra
- AMSR-E jitter contributes to some of this error
- some improvements expected with new mirror interpolation approach
- Early mission data needs special attention
- first 30 days is out of family
- larger than expected track error in first 150 days may be due to less accurate ephemeris
- Removal of remaining star tracker anomaly (125 msec readout time error in one star tracker) would help reach goal for future data

**Aqua LTT**

-  **Track direction**
- Linear trend smaller than Terra (10 vs. 15 m/year)
- Small cyclic variation (~10 m amplitude in Southern hemisphere)
-  **Scan direction**
- Linear trend larger than Terra (20 vs. 4 m/year)
- Cyclic variation primarily in Southern hemisphere (opposite hemisphere from Terra) and larger than Terra (20 vs. 11 m amplitude)

- Ancillary data: New BU Land/sea mask and Shuttle Radar Terrain Mission (SRTM) terrain data – both under evaluation
- Improved mirror motion model (approved for remainder of C4)
- New “GeolocationAccuracySuspect” flag based on list of maneuver times to help exclude data near/after maneuvers from science production
- Update Terra and Aqua LTT and implement ability to use solar elevation angle as surrogate for temperature to remove within-orbit variation (North/South hemispheric differences)
- Refresh GCP library to remove some points and to obtain a more global distribution using Landsat-7 GeoCover data set
- Consider reprocessing early mission definitive ephemeris data

- daily mean (dots) and standard deviation (bars)

- 16-day mean

**Acknowledgement**

- 16-day mean

- daily mean (dots) and standard deviation (bars)