# Presentation: 657829

## Anthony Colaprete

**Anthony Colaprete**

## Target Selection Criteria

**The four primary criteria for selection:**
- Terrestrial Observations (to insure minimum success requirements).
- Illumination of ejecta by sunlight
- Target properties (e.g., surface roughness, slopes, and regolith depth)
- Observed concentration of increased hydrogen

## Terrestrial Viewing Constraints

**Observatory Viewing Constraints:**
- Observatory needs to be 2hrs from dawn/dusk at impact
- Impact must occur when moon is more than 30 deg away from new moon or full moon
- Elevation angle of moon at impact relative to observatory must be greater than 45 deg
- Maximum impact time adjustment of 12hrs allowed (due to DV limitations)

## Ejecta Illumination

**Predicted NIR Spec Water Ice Sensitivity**

**To Earth**

**Shackleton**

**Shoemaker**

- Ejecta Illumination dominates sensitivity analysis.

## Optimum Target vs Launch Date 

- The optimum site varies with launch date due to changes in solar illumination angle and impact angle (from ARC-04.01.SciImpSite.01.v-3.0):

- The LCROSS Science Team recommends a target be selected for each possible LRO launch date and if possible all targets be limited to the South Pole.
- Furthermore, the LCROSS Science Team recommends new data be used to refine targeting up until 30 days prior to Centaur separation.

## Target Selection Process

**Target Selection Process**

**Selection Process:**

**Terrestrial**
**Observations**

**Hydrogen**

**Surface Properties**

**Ejecta Illumination**

**SC Water Sensitivity, RFA PL-CDA-02**

**Crater Selection**

***Craters A, B, C, or D***

***Craters A, B or D***

***Craters A or B***

***Crater B***

**Project Requirements**
**(e.g., dV)**

**New Data**

## Target Selection Process

**Target Selection Process**

## Selected Targets

**Selected Targets**

**Target Selection Products**
- Impact Site Selection Workshop, October 2006
- Impact Site Report from the Site Selection Committee: Impact Site Selection Committee Report (ISSCR) (November, 2006)
- LCROSS Science Team Impact site Position Report (STIPR) (January, 2007)
- Baseline Target Review (July, 2007)

- Campbell et al., 2007

## Selected Targets

- Sh

- Fa

**Selected Targets**

## Baseline 2008 Impact Sites

| # | Launch Date | Orbit Type | Impact Crater | Observatory | Meets: |
| --- | --- | --- | --- | --- | --- |
| 1. | 10/28/2008 | 3.5M | Faustini | Hawaii | A, B, C |
| 2. | 10/29/2008 | 3.5M | Faustini | Hawaii | A, B, C |
| 3. | 10/30/2008 | 3.5M | Shoemaker | Hawaii | A, B, C |
| 4. | 11/11/2008 | 3M | Faustini | Hawaii | A, B, C |
| 5. | 11/12/2008 | 3M | Faustini | Hawaii | A, B, C |
| 6. | 11/13/2008 | 3M | Shoemaker | Hawaii | A, B, C |
| 7. | 11/13/2008 | 3M | Shoemaker | Hawaii | A, B, C |
| 8. | 11/24/2008 | 3.5M | Faustini* | Hawaii | A, B |
| 9. | 11/25/2008 | 3.5M | Faustini* | Hawaii | A, B |
| 10. | 11/26/2008 | 3.5M | Faustini* | Hawaii | A, B |
| 11. | 11/27/2009 | 3.5M | Faustini* | Hawaii | A, B |

- A: Visibility to Earth
- B: Good sensitivity margin
- C: Knowledge of target properties

- * Faustini as selected when sensitivity margins in Shoemaker were low, and was selected over Shackleton due to its high sensitivity margins and knowledge of target properties.
- † Cabeaus was selected when all other target sensitivity margins where marginal or poor relative to the requirement or Cabeaus.

## Baseline 2008 Impact Sites

| # | Launch Date | Orbit Type | Impact Crater | Observatory | Meets: |
| --- | --- | --- | --- | --- | --- |
| 12. | 12/9/2008 | 3M | Faustini* | Hawaii | A, B |
| 13. | 12/10/2008 | 3M | Faustini* | Hawaii | A, B |
| 14. | 12/11/2008 | 3M | Faustini* | Hawaii | A, B |
| 15. | 12/12/2008 | 4M | Faustini* | Hawaii | A, B |
| *16. | 12/22/2008 | 4M | Cabeaus† | Chile | B |
| 17. | 12/23/2008 | 4M | Cabeaus† | Chile | A, B |
| 18. | 12/24/2008 | 4M | Cabeaus† | Chile | A, B |
| 19. | 12/25/2008 | 4M | Cabeaus† | Chile | A, B |

- A: Visibility to Earth
- B: Good sensitivity margin
- C: Knowledge of target properties

- * Faustini as selected when sensitivity margins in Shoemaker were low, and was selected over Shackleton due to its high sensitivity margins and knowledge of target properties.
- † Cabeaus was selected when all other target sensitivity margins where marginal or poor relative to the requirement or Cabeaus.

**Baseline 2008 Impact Sites**

## Target Refinement

- LCROSS retains the ability to change our target with the southern polar region (with about ~100 km of our original target):
- Target refinement within current targeted craters based on on-going analysis of existing data and analysis of new data (table below)
- Target refinement can occur as late as 30 days prior to impact date (e.g., for a 3 month cruise, approximately 60 days after launch).

## Target Selection

**Backup Slides**

## WEH, ISRU and the Sensitivity Requirement

|  | H2 Extraction |  |
| --- | --- | --- |
|  | Equator (100 ppm H)  | Pole (1 % water ice) |
| Specific Energy, kWh/kg | 2250 | 50.8 |
| Production Cost Ratio | 1 | 50-100 |

- Water content > 1-2% wt would constitute a more cost efficient than mining “dry” equatorial regolith

- The most recent water equivalent hydrogen (WEH) retrievals deconvolve the low resolution data set with models of the permanently shadowed regions (Elphic et al., 2007).
- The only estimates of WEH for individual craters
- Depends on the DEM to create shadowed regions
- Pervious estimates broadly (unconvolved) place WEH ~1%
- Several theoretical treatments place WEH ~1-2 %
- Radar returns associated with water ice requires volumetric scattering that places WEH limits > 20%

**For In-Situ Resource Utilization (ISRU), water concentrations of >1% make polar mining more efficient than equatorial mining.**
**This sets the ****required sensitivity of detection threshold of 0.5% (RFA PL-CDA-02).**

## Percent Water Sensitivity

- The sensitivity of the LCROSS SC nadir viewing NIR spectrometer was used as a verification of the Projects ability to sense regolith water.
- The Project must be sensitive to water concentrations of 0.5% wt (RFA PL-CDA-02).
- The NADIR NIR Spectrometer is the most sensitive instrument to ejecta cloud water ice, the expected dominant form of water initially within the ejecta cloud.
- The performance of the instrument was estimated using a discrete ordinate scattering algorithm (DISORT) and linear mixing of optical constants for water ice and dust.
- Water ice and dust opacities were estimated using impact model predictions.
- Instrument sensitivity was calculated using expected throughput and noise equivalent power (recent system level calibrations confirm this performance).
- For each impact date, several factors, which dominate measurement sensitivities to water ice, are taken into account in the model:
- Impact Angle
- Solar Illumination Angle
- Crater Wall Height
- Synthetic spectra for the first 30 seconds following impact are used to determine sensitivity for various concentrations of water ice in the regolith (see backup slides). While a complete error analysis has not been done, it is believed that these estimates are uncertain to approximately ±0.1 %

## Lunar Polar Hydrogen

- Crider & Vondrak, 2003

- Feldman et al., 2001

- 0
- 1
- 2
- 3
- 4
- 5

- Depth (m)

- 10-6     10-5      10-4      10-3      10-2

- [H] (wt. parts)

- Gardened
- Layer (1Byr)

- Desiccated
- Layer

- Space weathering homogenizes [H] at a rate of ~1.5 m per Gyr (Crider & Vondrak, 2003).
- Below ~2 m compaction greatly reduces pore space and reduces diffusive [H] capacity, however, burial is still possible.
- Impacts which excavate to ~1.5 m deep and have diameters of ~10 m occur on timescales of ~15 Myrs/km2, or about sixty 10 m craters km-2 on a surface 1 Gyrs old.
- This crater density results in a mean distance between **10 meter** diameter craters of **~150 meters** (or 450 meters for 100 Myo surface).
- Thus, H2O likely to be horizontally heterogeneous on scales of **~100** **m** to depths of ~1.5 m.

- Crater burial of “dry” material

## Lunar Polar Hydrogen

- If heterogeneity is controlled by 10 meter craters (crater excavation controlled), which are out of equilibrium with diffusive and space weathering processes, then the aerial fraction that *is* in equilibrium, i.e., “wet” is  ~1.-102/1002 = 99%.
- LP sensed the top meter (~70 cm) Derived LP values representative of this excavation controlled regolith “horizon”: high concentration pockets (WEH greater than few %) in the top meter *not* likely.
- Diffusive and space weathering processes likely to enforce their own horizontal modulation due to environmental effects (e.g., temperature and porosity)

**Lunar Polar Hydrogen**

_**D (m)     N**_
**40**
**    ****5**
**   ****1**
**0.1**
**80.    0.01**

**1 km**

**1 km**

**D~10 meter **

**For a 100 Myr Old Surface:**

## Apollo 11 Craters

**East Crater ~30 meters**

**Apollo 11 Craters**

**West Crater ~200 meters**

**1.2 km**

**1.0 km**