# Presentation: 522971

## Preliminary Analysis of the Absolute Cartographic Accuracy of the Clementine UVVIS Mosaic

**A.C. Cook****[1]****, M.S. Robinson****[2]****, B. Semenov****[3]****, and T.R. Watters****[4]**

**[1] School of Computer Science & IT, University of Nottingham, UK (Email: acc@cs.nott.ac.uk) **
**[2] Department of Geological Sciences, Northwestern University, Evanston, IL, USA (Email: robinson@earth.northwestern.edu)**
**[3] Jet Propulsion Laboratory, Pasadena, USA (Email: boris.semenov@jpl.nasa.gov)**
**[4] Center for Earth & Planetary Studies, National Air & Space Museum, Washington D.C., USA (Email: twatters@nasm.si.edu)**

***Thanks to M. Rosiek and D. Cook USGS Astrogeology***** **

## Problem: Evaluating absolute accuracy of Clementine 750 nm basemap

**43,000 images**
**265,000 match-points**
**ground truth from “Apollo zone”, all of farside floats**
**no topography used, assumed spherical Moon of 1737.4 km**
**spacecraft position **
**doppler tracking**
**gravity models**

## Validate the Farside?(cartographic sense)

**Recently completed global stereo based topo map**
**Used original archived SPICE files (not USGS/Rand control net)**
**Overlaid the topo with basemap and found large offsets**

- Clementine stereo topo on 750 nm basemap

## 750nm Basemap Geometric Accuracy?

**Farside**

**Farside**

**Offset Map: Is this a map of absolute accuracy (lat/lon)?**

## Spacecraft Position (SPK)

**Small difference in SPK files**
**Polar tilt constant differs by 0.022°**
**Histogram of sub-spacecraft point differences (max 1 km)**

**SPK: Cannot explain the**
**observed offsets**

## Camera Pointing (CK)

**USGS/Rand control net should be different than the archived CK (that’s what was updated)**
**And it is! But are these offsets reasonable???**
**Histogram shows differences USGS/Rand and archived CK (image center points for all 43,000 images in control net)**
**Image strips overlap by 10-20 pixels (1-2 km near eq)**

## Camera Pointing offsets

**Nearside Apollo zone generally good agreement (<2 km)**
**Should be same order for whole Moon otherwise gores between orbits would have occurred**
**Outside Apollo zone there were no absolute control points (none exist)**
**Control net allowed adjustments up to 10x the accuracy of the spacecraft pointing - is this reasonable?**

## Simple Cylindrical Projection of Differences in Image Centers from Archived CK & USGS/RAND Control Network

**Image bore-sight offsets (km)**

**SPA**

## What’s Up?

**No absolute control outside the “Apollo Zone”**
**Spherical Moon (1737.4km) when in reality there are ******** 10 km topographic excursions (SPA and near Korolev crater)**
**Clementine periselene ~400 km**
****** ****10 km translates to ********2.5% error in pixel scale**** **
**The lack of control outside Apollo zone results in extrapolation across hundreds of orbits and thousands of images, of these images pixel scale exhibits low frequency error term.**** **

## Where are we?

**We **_**believe**_** that the offset map indicates there is a low-frequency error term in the control network which is not in line with the reported 500m absolute accuracy of the basemap (except in the Apollo zone).**
**We **_**believe**_** the offset should be 1-2 km everywhere, in line with the accuracy of spacecraft pointing, perhaps a little larger in areas with no direct radio tracking on the central farside.**
**We **_**do not know**_** of an unambiguous way to solve this problem with the existing data. Redoing the control network using  the low frequency Clementine LIDAR map may improve the solution somewhat-to-considerably. Still - there is no absolute control for >50% of the Moon.**

## Summary

**Mert Davies had for years cobbled together diverse data of the Moon to make best possible effort at creating lunar control network (Telescopic, LO, Mariner 10, Galileo, Clementine)**
**We **_**desperately**_** need a dedicated geodesy mission**
**SPA sample return will have to deal with **_**possible**_** positional errors of 10-20 km**