# Presentation: 947459

## MRO’s High Resolution Imaging Science Experiment: Science Expectations

**Alfred McEwen, Candy Hansen, Nathan Bridges, Alan Delamere, Eric Eliason, John Grant, Ginny Gulick, Ken Herkenhoff, Laszlo Keszthelyi, Randy Kirk, Mike Mellon, Peter Smith, Steve Squyres, Nick Thomas, Cathy Weitz**
**6th International Mars Conference**
**Pasadena, CA July 21-25 2003**

## MRO and HiRISE Capabilities

- The **Mars Reconnaissance Orbiter (MRO)** is expected to launch in August 2005, arrive at Mars in March 2006, and begin the primary science phase in November 2006.  MRO will carry a suite of remote-sensing instruments and is designed to routinely point off-nadir to precisely target locations on Mars for high-resolution observations.  The mission will have a much higher data return than any previous planetary mission, with 34 Tb of returned data expected in the first Mars year in the mapping orbit.   The mapping orbit is nearly polar, 255 x 320 km above the surface, 12 orbits per day.

**HiRISE Capabilities**

## Comparison of Remote Sensing by MGS, Mars Odyssey, Mars Express (MEX), and MRO

***Comparison of Remote Sensing by MGS, Mars Odyssey, Mars Express (MEX), and MRO***

*Spatial*
_*Scale*_
- 1 km
- 300 m
- 100 m
- 30 m
- 10 m
- 3 m
- 1m
- 0.3 m

***ODY*****-THEMIS**

- Visible              Visible - Near Infrared                Thermal

*Wavelength (microns)*

**CRISM**

**HiRISE**

***MEX*****-OMEGA**

**CRISM-*****Survey***

***MGS*****-TES**

**CX**

**THEMIS-VIS**
**MEX-HRSC**
**MRO-CTX**
**MGS-MOC**

## MRO High-Resolution Observing Block

- ~45 km

- 30 km

***CTX ***

- 20 km

- 10 km

***CRISM ***

***HiRISE ***

**Image Sizes when Viewing from 300 km**

## Why HiRISE?

**Science potential of high-resolution imaging from orbit demonstrated by MGS Mars Orbital Camera (MOC; Malin and Edgett, 2001).**
**HiRISE is a significant improvement over other Mars imaging experiments:**
- Ground Sampling Dimension 5 times better than MOC (0.3 versus 1.5 m/pixel)
- Swath Width: 6 km rather than 3 km of MOC
- Signal:Noise Ratio >100:1 (better than MOC at full resolution)
- Color imaging:
- 60 times higher resolution than THEMIS
- 15 times higher resolution than HRSC
- Time of day: 3 PM LMST rather than 2 PM (MGS), better topographic shading.
- Stereo imaging with pointing knowledge needed to produce Digital Elevation Models (DEMs) with vertical precision ~20 cm; 30 times higher resolution than HRSC.

- Downstream tip of layered streamlined mesa in Athabasca Valles (M11-00331).

## Simulation of a HiRISE image over a portion of the Grand Canyon.  View is from 500 km range; MRO’s Primary Science Orbit will be 255 x 320 km, so swath width over Mars will be from 5.1 to 6.4 km.  (A) Landsat image showing the swath width, nominal length (could be up to 65,000 pixels), and color coverage. The blowup (B) is an air photo showing the location of (C), a simulated HiRISE image (50cm/pixel) incorporating the predicted telescope performance (MTF).

## HiRISE Focal Plane Assembly

- 14 CCDs (2048 x 128 pixels):
- 10 CCDs Form Red Channel (20,000 pixels)
- 2 CCDs Form Blue-Green Channel (4000 pixels)
- 2 CCDs Form NIR Channel (4000 pixels)

**Notes:**
14 CCDs staggered 

## Science Themes for Target Prioritization

## Science Priorities 

**MRO Level 1 Science Requirements:**
- _High-Resolution Imaging Science Experiment (HiRISE) _
- Ability to resolve 1-meter-scale objects and differences in surface morphology
- Swath width greater than 3.5 km *(HiRISE has 20,000 pixels for 6 km swath width at 300 km altitude)*
- Signal to noise ratio of order 50 to 1 or more *(HiRISE requirement is >100:1 SNR*)
- When required, stereo imaging is achieved using observations on different orbit passes.
- The MRO shall acquire data sets from 2 or more of its instruments for characterization of targeted sites, **including high-resolution imaging data needed to certify these sites with respect to landing site hazards and to support the planning of surface operations, including surface mobility.  **
- HiRISE interpretation: Stereo-derived Digital Elevation Models (DEMs) with ≤0.5 m vertical precision are needed both to certify landing safety and to support planning of surface operations.

- HiRISE Science Priorities:
- 1. Achieve 1-meter spatial resolution with swath width > 3.5 km.  (Explicit Level 1 science requirements.)
- 2.  Achieve <0.5 m stereo vertical precision.  (Interpretation of Level 1 science requirement.)
- 3.  Distinguish and measure color and albedo variations

- Right: Topographic model with 10-m contours of Mars residual south polar cap (Soderblom, Kirk, and Herkenhoff, 2002).

## What is the expected performance?

- 	If Spacecraft jitter is minimal, HiRISE images will have an excellent PSF as well as high SNR.   The PSF does have broad wings in part due to the backside-illuminated CCDs, but the greater sensitivity (compared to more standard frontside-illuminated CCDs) will enable us to choose shorter TDI times and better minimize smear from spacecraft jitter.

- Synthetic 30 cm/pixel image of a boulder 90 cm diameter, 45 cm high, 45° illumination

- Image convolved with camera PSF and s/c jitter 1 pixel cross-track and 0.5 pixel down-track; 1% noise added

- Image deconvolved via PSF with 10% error, to simulate imperfect knowledge of PSF. Noise is enhanced but this can be minimized with Weiner filter.

## HiRISE color imaging will facilitate stratigraphic interpretations of compositional units identified by CRISM and other experiments. 

- IKONOS image of sedimentary layers near Moab Utah, 4 m/pixel.

**HiRISE color imaging will facilitate stratigraphic interpretations of compositional units identified by CRISM and other experiments.**

## Geometric Reconstruction Is Essential to Stereo Measurements

- Image at left is an anaglyph of the simulated 48-pixel overlap with LMA jitter model (worst time period).
- Colors indicate false topography (i.e., without geometric reconstruction).
- Preliminary results of simulations show high correlation accuracy for  48 x 48 pixel overlaps.

**Spacecraft Jitter: What’s the Problem?**
- TDI imaging with 1 radian IFOV is very sensitive to spacecraft motions:
- Motion over time scales up to 12.7 msec broadens the Point Spread Function (PSF) and reduces spatial resolution.
- Motion over all time scales up to that of the full image (up to 6.5 s at full resolution) distorts the image geometry.   These distortions are significant to stereo analyses and must be corrected to ~1/3 pixel to achieve 0.5 m vertical precision.

- Synthetic oblique view of Gusev Crater, derived from DEM by R. Kirk.

## POINTING DISTURBANCE SOURCES

- HiRISE

- CRISM
- Compact Reconnaissance
- Imaging Spectrometer for Mars

- Reaction
- Wheels

- Solar Array

- Solar Array

- High-Gain
- Antenna

- MCS
- Mars Climate
- Sounder

- IMU  Inertial
- Measurement Unit
- (Not shown)

## Jitter Simulations

## Jitter and Geometry Knowledge from CCD Layout

- Ground features in image data are correlated between overlapping pairs or triplets of CCDs.
- 7.3 mm offsets are too large (608 rows or lines), so selected CCDs (see arrows) are offset by 32 rows (384 μm) and 3 CCDs are needed per solution.
- There are 5 triplets of CCDs for 32-line solutions (1-2-3, 3-4-5, 5-6-7, 7-8-9, 8-9-10).
- Some solutions could fail for lack of surface features or data gaps within 48 x 48 pixel areas.
- Red CCD overlaps only 48 pixels wide.  NIR and Blue-Green CCD overlaps of 4000 pixels provide high-reliability solutions every 1250 lines.
- Solutions allow us to model the broadening of the PSF both cross-track and along-track to an accuracy of 1/5 pixel or better.

## Stereo Data Acquisition

- Stereo imaging a high science priority: Plan to acquire ~1000 pairs
- 1/2 at full resolution
- 1/2 at 2x2 summation
- DEM horizontal resolution
- ~5 pixels
**~1.5 m** at full res
- DEM vertical precision
- ~0.2 pixel / (Base/Height)
**~0.2 m** for 1+2=15°, full res
- Require 1+2=15° to 30°
- Avoid looking too far east  (low phase angles bad for stereo)

## Production of Digital Elevation Models (DEMs)

- Work will be led by R. Kirk at USGS/Flagstaff.
- Integrated Software for Imagers and Spectrometers (ISIS) used to correct image geometry.
- Commercial photogrammetry software (SOCET SET) used to produce DEM.
- ISIS/SOCET synergy is especially important for correcting errors in image orientation, which include
- high frequency vibrations (“jitter”) —> undulations of DEM
- absolute pointing/position errors —> offsets of DEM from true location

**In ISIS**
- HiJITTER: estimate pointing jitter by automatic matching of overlapping areas of CCD images; compare/combine with gyro data
- HiGEOM: resample image data to remove jitter effects; also remove optical distortion & knit CCDs together into one image

## High-Resolution DEMs Will Enable Quantitative Geomorphology

- Controls on bedrock incision in the Grand Canyon are being studied with high-resolution DEMs by J. Pelletier et al.; see http://geomorphology.geo.arizona.edu//geomorphology.html

- Other things being equal, one effect of lithology is to increase stream gradients in strongly resistant bedrock such as in Hack's classic example of steeper gradients in sandstone than in shale of the Shenandoah Valley, Virginia.   (From J. Pelletier’s class notes for Introduction to Geomorphology.)

## High-resolutions DEMs may be essential to some compositional interpretations of CRISM

- Robinson and Jollif (2002) used  a high-resolution DEM of the Apollo 17 landing site to correct the photometry of Clementine multispectral data.   Spectral parameters that correlate with FeO and TiO2 abundances on the Moon changed significantly over steep slopes following the topographic correction.   Topographic effects on reflectance spectra may be more severe on Mars due to the effects of red skylight.  End-member compositions (i.e., bedrock) may be best exposed on steep slopes, so these areas are of great interest.

## Key Science Issues for HiRISE

- Is there water near the surface today?
- Origin of gullies
- Ages of gullies, dunes, patterned ground
- When and where have there been long-lived bodies of water?
- Oceans, lakes?
- What is the total inventory of water and how has it cycled?
- Flood discharges, volcanic processes
- How has climate varied?
- Polar layers, CO2 inventory
- Were there thick ice sheets?

**Landing Sites:**
- Past Landing sites: Viking, Pathfinder, MER, Beagle-2
-  Detailed orbital views may solve mysteries, lead to new interpretations
- Future landing sites
-  Candidate landing site evaluations for Phoenix, MSL, sample return?
- Active surface missions during MRO
-  MSL, Phoenix?
-  Electra relay on MRO
- Meter-scale topography will be essential to evaluate landing hazards and rover trafficability.

- Lakes and seas on Mars: Fact or Fantasy?  (Image from http://www.cascadia.ctc.edu/facultyweb/instructors/jvanleer/terra%20mars/final_product.htm)

## Pathfinder: Are 1-2 m high ridges due to 2-3 billion years old fluvial morphology?

- Are these ridges due to the Ares Valles floods (Golombek et al., 1999) or more recent eolian modification (Greeley et al., 2000)?   MOC images do not enable a clear distinction because the resolution is too low, and Pathfinder images do not cover sufficient area.  M11-2414

## Mid-Latitude Gullies

- Origin of gullies:
- Groundwater
- Snowmelt
- Age of gullies
- Currently forming?

**How recently did the gullies form?   **Malin and Edgett [2000] proposed that the gullies are young (probably less than 106 yrs) because there are usually no superimposed impact craters and because gully materials are superimposed over dunes and polygonally-patterned ground, which are young features on Earth (103 to 106 yrs for patterned ground--Sletten et al., 2003).  This leaves open the possibility that gullies are forming today, and that liquid water may exist very near the surface.   HiRISE can search for changes in the surface topography (compared with previous MOC or HiRISE images) that would indicate current activity of gullies.  Evidence for current formation rates of dunes or patterned ground would also help address this issue.

- Credit: MSSS.com

## Repeat Imaging of Gullies: best to match seasons to detect changes, or use DEMs to simulate any viewing/illumination

- Credit: MSSS.com

## Age Constraints on Gullies

**1. Lack of small craters:**
- Are most small craters on Mars primary or secondary craters (McEwen, 2003)?  If primaries, the absence of craters imply a maximum age of a few million years.  If secondaries, age limit may be closer to 100 million years.
**2. They are younger than other “young” landforms.**
- Gully deposits are  superimposed over dunes and patterned ground--but how old are those features?   At what rate do these features form on Mars?  Repeat imaging by HiRISE will be used to constrain the rates of current processes.

- Credit: MSSS.com

## Origin(s) of Layered Sedimentary Rocks

**Have there been long-lived bodies of water on Mars?  **
- Origin(s) of fine layered deposits key to this debate.
- Leading contenders are lake deposits or eolian/airfall deposits.
- HiRISE can detect finer details, but cannot resolve particle sizes.
- Maybe HiRISE can detect diagnostic structures such as eolian cross-bedding.
- HiRISE DEMs will tell us if the layers are horizontal or draped over pre-existing topography.
- Convincing interpretations may be possible by combining CRISM and HiRISE observations and with ground truth from MER.

- Right: Cross-bedding in dunes (credit: A. Howard)

- Credit: MSSS.com

## Origin of Vastitas Borealis Formation

- Surface layer buries cratered northern plains.
- Many interpretations have been published.
- If ocean sediments, should be fine-grained except for ice-rafted boulders
- Presence of meter-scale rocks would be more consistent with flood deposits.

- Possible outlines of northern oceans.  Credit: MOLA team and Head et al. (1999).

## Glaciation on Mars?

- Large-scale glaciation [Kargel and Strom, 1992] requires atmospheric transport of large quantities of water, and implies that major climatic change has occurred.  Glacial moraines are very poorly-sorted deposits including large boulders, which should be discernable to HiRISE.   Are the ridges west of Arsia Mons (right) glacial moraines?  (THEMIS visible image, 18 m/pixel; image ~18 km wide).

## Volcano-Water and Volcano-Climate Interactions

- 	Possible rootless cones on Mars (M08-1962).  Rootless cones form when lava interacts with water under the flow, and are not primary vents for lava.

- Rows of lava cones lining the fissure from which the Laki lava flow erupted in 1783-1784 in Iceland. This was the largest lava eruption for which detailed written records exist, but was tiny compared with geologically recent Martian eruptions. The gases from this eruption cooled the climate across the entire Northern Hemisphere (Thordarson et al., 1996).  The cones in this picture are about 10 meters tall (30 feet).

## Fluvial              Deposits

- Possible subaqueous dunes in Athabasca Valles
- Detection of meter-scale rocks would prove dunes are not eolian
- MOC has detected few boulders in channels, but can only detect unusually large boulders (>5 m diameter)

**Hydrology: How much water was released?   **The outflow channels clearly had enormous peak discharge rates (Q), but estimates of Q differ by orders of magnitude.  One key morphology that helped to constrain the hydrology of the Channeled Scablands floods was the occurrence and properties of subaqueous dunes (also called “giant current ripples”).  Some excellent candidates for subaqueous dunes have been identified in Athabasca Valles (Burr et al., 2002), but it is not yet possible to prove that these are not eolian dunes.  If HiRISE detects boulders in the dunes, then we will know that the transport medium was water, not air.

**Where are the boulders?** MOC has detected very few boulders in Martian channels, but that may be a resolution limit and HiRISE could detect many boulder deposits.  Slowly-cooled lava flows tend to quickly disaggregate along joints into ~1- or 2-meter sized blocks.  If there are larger boulders, HiRISE will enable some characterization of the degree of rounding, which is related to transport distance.  HiRISE color images could enable tracing boulders back to their source regions.  In addition, HiRISE topographic data will enable detailed hydraulic modeling.

## Polar Layers and Climate History

- 	Most Mars researchers believe that the polar layered deposits are the result of variations in the amounts of dust and water ice deposited over many climate cycles, but the amount of time needed to form individual layers remains a major uncertainty. Studies of the thickness of polar layers are limited by image resolution and color data is needed to distinguish dust, ice, and sand.  Analysis of HiRISE data should result in a better understanding of the timescales involved in the deposition of the layered deposits and provide important information regarding the climate history of Mars.

## Monitoring Yearly Changes in S. Polar Residual CO2 Cap

**	****What is the polar CO****2**** inventory?**  The “swiss cheese” terrain on the residual south polar ice cap has been observed to retreat 1 to 3 meters in 1 Mars year, apparently via sublimation of CO2 ice (Malin et al., 2001).  Continued monitoring of these changes and high-resolution topographic measurements will enable us to better quantify rates of CO2 loss and the total CO2 inventory available to facilitate periodic climate change.

## New Discoveries

- Anything MOC can do, HiRISE can do better, except doing it first!
- The most important new results from HiRISE will be new discoveries: features and phenomena not yet detected on Mars.

- References
- Burr, D.M., et al. (2002) Icarus 159, 53-73.
- Golombek, M.P., et al. (1999) J. Geophys. Res. 104, 8523-8553.
- Greeley, R., et al. (2000) J. Geophys. Res. 105, 1829-1840.
- Head, J.W. et al. (1999) Science 286, 2134-2137.
- Kargel, J.S., and Strom, R.G. (1992) Geology 20, 3-7.
- Malin, M.C., Caplinger, M.A., and Davis, S.D. (2001) Science 294, 2146-
-      2148.
- Malin. M.C., and K.E. Edgett (2000) Science 288, 2330-2334.
- Malin, M.C. and Edgett K.S. (2001) J. Geophys. Res. 106, 23,429-23,570.
- McEwen, A.S., (2003) 6th International Conference on Mars.
- Mustard, J. et al. (2001) nature 412, 411-414.
- Robinson, M.S., and Jollif, B.L. (2002) J. Geophys. Res. 107/E11, paper
-      20.
- Sletten, R.S., Hallet, B., and Fletcher, R.S. (2003) J. Geophys. Res.-Planets
-      108/E4, paper GDS 25.
- Soderblom, L.A., Kirk, R.L., and Herkenhoff, K.E (2002) LPSC abstract
-      1254.
- Thordarson, Th., et al. (1996) Bull. Volcanol. 58, 205-225.

- Recent surface mantle poleward of 30 latitudes [Mustard et al., 2001] (M20-00144)

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