Sunday, July 29, 2012

Europe's Lunar Lander

All illustrations credit: European Space Agency

The European Space Agency (ESA) is moving to approve its first lunar landing mission.  While the mission will carry out some science, the primary goals of the mission will be to fully develop and demonstrate autonomous landing in the rugged terrain near the moon’s south pole.

The lander will use only its autopilot while descending over rough terrain.  The craft’s computer will compare images it takes and it descends along with terrain maps generated with LiDAR to maps stored in its memory.  By recognizing landmarks, the lander’s computers will adjust direction and descent speed to safely descend toward an preselected landing area.  The final landing location will be selected by the craft itself to avoid boulders, steep slopes, and shadows that would prevent its solar panels from generating power. 

Once on the surface, the lander will become a science station.  While previous lunar landers have stayed near the lunar tropics (all landed within 40 degrees of the equator), this mission will explore a new region and possibly new soil types.  The landing zone will be at the edge of the largest impact basin in the Solar System, the Aitken Basin.  Mission planners hope that the instruments will sample soils and rocks thrown up from the lower lunar crust and mantle.  Another set of instruments will explore the interaction of the plasma environment at the lunar surface with the omnipresent lunar dust.

Planning documents talk about a nominal surface mission of 14 days following landing in the sunlight when the primary science will be conducted.  That will be followed by 14 days of night in which the lander will use its batteries to keep essential systems from failing in the chill.  Mission planners plan to reacquired communications with the lander with sunrise, and the mission could potentially last for a number of months.

Approval of the mission is expected this fall by ESA.  Landing is planned for 2018.

Editorial Thoughts:  In many respects, this mission has similar goals to NASA’s Mars Pathfinder mission that landed in 1997.    The Pathfinder mission allowed NASA to prove the technology for landing smaller than flagship-scale missions on Mars.  The entry, descent, and landing technologies developed for that mission directly enabled the landing of the Mars Exploration Rovers Spirit and Opportunity in 2004.  Several teams are proposing future rover missions that would land on Mars using Pathfinder’s airbag technologies.  (NASA later developed a second Mars EDL system for small stationary landers for the Phoenix mission that may serve as the platform for the InSight mission currently in competition for selection as the next Discovery mission.) 

ESA’s ExoMars was initially conceived as a technology development and demonstration mission, although it has become primarily a science mission as its definition firmed.  Aspects of the original goal remain with a demonstration lander in 2016 that will prove a landing system for future Mars missions.

I believe that the pictures taken by the lander may prove to be some of the most iconic of the space age.  The Earth will lie close to the horizon,  ensuring that images will capture the mountainous landscape of the lunar southern polar region with the Earth hovering just above.  We may again see our world as a fragile oasis and as part of a double planet system.

For more information:

Technical information prepared for scientific teams proposing instruments: (see pdf downloads in right column)

Thursday, July 26, 2012

Updating While Waiting: The Dilemma

Those of us who follow the plans for future planetary exploration are waiting for two breaking events.  The first, expected in July based on NASA’s previously announced schedule but subject to delay, is the announcement of which mission it has selected for the Discovery mission.  Either the interior of Mars, the heterogeneity of a comet, or the surface of a Titan lake will be the focus of a great mission.  (It may say something about what kind of person that I am, but whatever is announced, I will feel that two great opportunities have been passed over.)

The second event, with a firm schedule down to the minute, will be the success or failure of the Curiosity rover’s landing on Mars.  While this may seem like current rather than future planetary exploration, a success will encourage more funding for planetary missions while a failure will do the opposite. quotes the head of NASA’s planetary science program on the importance of this landing in a speech given to lunar scientists, “’It’s absolutely essential for everybody in this room to recognize that, whether you’ve been following this or not, this is going to have an enormous effect on you, personally,” he [Jim Green] told a room filled primarily with lunar scientists. “Whether it’s successful or not successful, it will have an enormous effect on the planetary budget, and therefore, all of our careers… The landing of MSL will be absolutely critical, and we really need to take note of what’s going to happen here.”  

So while we wait, I thought I’d provide updates in this post and following ones on a number of items that don’t quite deserve a post of their own.

First up, published today, is a long article in the journal Science on the options for exploring Mars.  (Unfortunately, it’s subscription only or can be purchased for $15.  You can read the first paragraph and follow the link to purchase.)  Richard Kerr reports on the quandary that the Mars program finds itself in.  With the exception of sample return and the exploration of Mars’ interior (the focus of one of the Discovery missions in competition), all the major firsts for Mars have been done (assuming the Curiosity mission is a success).  So while future orbiters could carry better versions of instruments and rovers could land in new places, the feeling is that the results wouldn’t be revolutionary enough to compete with missions to other worlds.  Kerr quotes the head of the Decadal Survey’s Mars panel on the value of future incremental missions: “[Phillip] Christensen [ Arizona State University, Tempe] says he would love to fly a souped-up version of the instrument [a better multispectral imager] on a future [orbiter] mission. “But is that essential to our understanding of Mars? I think not,” he says. “It wouldn't be revolutionizing. You can do only so much from orbit, no matter how good your spectrometer. We're pretty darn close to doing what you can from orbit.” 

Kerr points out that other scientists disagree with Christensen’s (and many others) view on the value of incremental missions.  John Grotzinger, the Curiosity rover’s project scientist, for example, is promoting the idea of a series of smaller rovers in the class of the Opportunity rover currently at Mars but with significantly more advanced instruments (see below). 

Kerr ends his article by pointing out that NASA’s Mars program is becoming entangled with NASA’s human spaceflight program, which has a long term goal of reaching Mars.  He finishes the article with an assessment of the risks of this strategy: “In other words, planetary science would be riding human exploration's coattails to Mars in the FY 2014 budget request. ‘That is fraught with danger,’ Christensen says. ‘If you attach yourselves to human exploration,’ [Frances] Bagenal [University of Colorado, Boulder] says, ‘you end up tailoring your science to address the needs of human exploration. Then they change their mind. The lunar people have been down that road several times.’”

Another article out this week from the journal Nature, explores the idea behind what an incremental rover mission might do.  (Nature made this article freely available here.)  In a previous post, I described ideas for reusing the basic design of the Mars Exploration Rovers Spirit and Opportunity and outfitting them with modern instrument suites (a lot of instrument development has occurred since Spirit and Opportunity were designed).  One idea would be outfit one or more rovers with a new generation of instruments that can date Martian rocks to within a few tens of millions of years.  The article explains how important these measurements would be, “If chronology on the Moon is still uncertain, then Mars is a mess. The crater-count method does not work as well there, mainly because the wind, water and frost that sculpt the surface also erase craters… With a portable system, researchers could decipher how long volcanism lasted on Mars and when it stopped. They could find out when the planet's warm, wet and possibly habitable environment gave way to the cold desert it has been for several billion years. ‘If any evidence is found for life, we sure as heck will want to know when it was there,” says [Hap] McSween [University of Tennessee in Knoxville].’”  

The article provides a fascinating insight into the process and challenges of developing cutting edge capabilities for new planetary missions.  I highly recommend it.

Editorial Thoughts: These two articles together highlight a tension in how science is done.  The easiest way to make big discoveries is to simply be the first to go somewhere (or at least be the first to bring a new type of instrument such as the first high resolution imaging spectrometers in Mars orbit).  The naturalists who explored the world during the European age of discovery had a field day.  Everywhere they went, there was a new discovery waiting for them.  (To get an idea of what the opportunity was like, look up how many species the Scottish naturalist David Douglas named for himself or had named for him in the Pacific coast states of the U.S.  However, it has taken decades of intensive science to follow up on these discoveries and to start to really understand the geology, biology, and ecology of these areas.  In the Pacific Northwest, where Douglas was an early European explorer, we didn’t even understand the ecological importance of old-growth forests until the last two to three decades, and my colleagues are still trying to understand many key facts how the develop and function.

Planetary science has been in the lucky position of those European naturalists in being able to make many astounding discoveries simply by delivering a spacecraft or an instrument to a new place.  The opportunity for those relatively cheap and frequent missions becomes fewer with each new mission.  As a result, the planetary community is left to decide whether to recommend less expensive missions that do the yeomen’s work of filling in the details or propose the often expensive bigger missions that do the new and extraordinary.  I believe that the fear is that the politicians may balk at paying hundreds of millions of dollars per mission for the former and equally may balk at paying billions of dollars for the latter.

Monday, July 23, 2012

Joint MOONRISE - ORION Mission to the Lunar Farside

Phil  Horzempa returns with another post, this one on an interesting idea for a first joint human-robotic mission to the far side of the moon.  

I've just finished a revision to a paper, so I will have more time to post in the near future.


   The Moonrise robotic sample return mission has been proposed several times as a New Frontiers effort.  Van discussed some of the aspects of the mission in previous posts. Recently, the Moonrise team has released more details of how the mission would be conducted.  I will first review those aspects, before considering a new twist to this mission involving possible participation by NASA's manned spaceflight program. 

Figure 1

Figure 2

    The Barcelona report (1) is the first detailed public disclosure of Moonrise's mission and spacecraft design.   Figure 1 shows the outline of the mission operations.  Since Moonrise is designed to return samples from the Far Side of the Moon, it requires a relay element which is provided by a mini-comsat.  Note that both the lander and the relay go through the Lunar L2 location on the way to their target.  This is perhaps to save fuel and to "wring-out" the craft before the events surrounding sample acquisition.  The Moonrise team has picked a landing site near the Bose crater within the South Pole - Aitken Basin on the Far Side. (Figure 2)

Figure 3

   Figure 3 shows the entire launch package.  Note the large SRM (Solid Rocket Motor) required to cancel most of the lander's velocity as it descends from LL2 to the Moon's surface.  It appears that the Moonrise lander and its descent sequence are very similar to that of the Surveyor landers of the 1960's.   After retro-fire is complete, the large SRM is ejected, with final approach, and velocity cancellation, handled by vernier thrusters. 

Figure 4

   The lander spends 10 days on the lunar surface, utilizing a scoop to gather samples.  There is a sieve on the scoop so that a larger number of small rocks are collected.  The lander is solar-powered, requiring that the surface mission be accomplished within the 2-week-long lunar day.  With the completion of sample acquisition, the LAV (Lunar Ascent Vehicle) is launched. (Figure 4)  The Earth-return capsule may go through the LL2 on its journey, again perhaps to save fuel. 

   The Moonrise proposal was down-selected as a finalist in the last 2 New Frontiers competitions, but was not chosen to proceed to flight.  It seems likely that it will again be put forward for the next NF AO (Announcement of Opportunity).  However, recently, a new approach to collecting samples from the Moon's Far Side has been proposed. 

   With the arrival of the Orion manned exploration capsule in a few years, it is possible that it could join an unmanned Moonrise mission to collect lunar samples.  In this new approach, the Orion would fly to the Lunar L2 location and "hover" there for 1 - 6 months.  The astronaut crew would not land on the Moon, but would tele-operate an unmanned rover on the Moon's Farside.  It seems that details have not been fleshed-out, but let me suggest one scenario.  A Moonrise lander could be dispatched to a landing on the Farside, delivering the tele-operated rover.  If the Moonrise mission were flown in conjunction with a manned Orion mission, then the relay comsat and Earth-return capsule could be deleted from the Moonrise payload, freeing up mass needed to accommodate the  rover.   This surface mission would still need to be completed within 10 days because of thermal and solar-power restrictions.  However, the tele-presence of humans would greatly assist the collection of samples.  One could imagine a long-term surface mission lasting several months, but that would call for a lander modified for the 2-week-long ultra-cold lunar nights. 

Figure 5

   Just recently, at the 5th Lunar Science Forum, Jack Burns spoke about an Orion mission to the Lunar L2 location (2).  A diagram of such a mission, from an earlier proposal by Burns, is shown in Figure 5.  At the Lunar Science Forum, he presented a modified version of this mission that would see the Orion crew "settling in" at the LL2 location for about 90 days, instead of the 15 days indicated in Fig. 5.  In addition, Burns hinted that such a manned mission could include the task of collecting lunar samples delivered to the LL2 location by a Moonrise-type vehicle.  He pointed out that this mission would return to Earth with lunar samples without needing to actually land a crew on the surface.  Once the sample collection phase of the Moonrise mission was complete, the rover would still remain on the Moon's surface, available to pursue more exploration, guided by the Orion crew at LL2. 

   This hypothetical mission between NASA's Science Mission Directorate and Human Space Flight, could serve as a dry-run for a similar joint sample-collection effort at Mars, as described in my post of July 5, 2012.  The Martian mission would see an astronaut crew collecting samples launched into orbit around Mars by unmanned precursors.  As with the L2-Farside mission, that crew could also tele-operate a rover to gather additional samples.  The L2-Farside mission could serve as a valuable precursor for such a Mars mission.  To quote from a Lockheed-Martin document (3), "The lunar L2-Farside missions will develop and practice operational methods for this type of human/robot exploration."  So, as NASA pushes towards developing the experience base required for a manned Mars mission, we may see valuable lunar science data obtained along the way. 

Philip Horzempa 


3.  "Early Human L-2Farside Missions" by Lockheed-Martin Corporation

Tuesday, July 17, 2012

Caught in a Squeeze

Sometime in the next two weeks, NASA should announce the selection of the next Discovery mission to either Mars (Insight geophysical lander), a comet (CHOPPER), or the lakes of Titan (TiME).  The journal Nature’s website has a good summary of the mission candidates (as, I hope, this blog does here).  Nature also published an analysis of the Discovery program with sobering implications.  The last selection of a Discovery mission (the twin GRAIL orbiters currently studying the interior of the moon) was five years ago.  With the currently planned budgets, the next selection of a Discovery mission will come approximately five years hence. 

A two-per-decade cadence of Discovery missions is not what was originally planned for the program. The program was envisioned as a frequent series of relatively inexpensive missions that allowed an  element of risk not possible in more expensive missions.  As the first figure below shows, the early missions fulfilled that goal with a rapid clip of missions costing less than $340M.  Over time, however, the complexity of missions has increased with commensurate increase in mission costs (see the second figure).   Given tight budgets, the result has been to spread out the selection of new missions with, as mentioned above, five years between the selection of the GRAIL mission launched last year and the previous mission.

Discovery mission costs by year of launch.  
The Discovery 12 mission will be the one selected this summer.  
Data from the Nature article based on data from the Aerospace Corporation.

Discovery mission cost relative to mission complexity.  
Data from the Nature article based on data from the Aerospace Corporation.

Last year’s planetary Decadal Survey recognized both the problem of too few missions and the increasing complexity of missions.  It recommended that the frequency of missions be increased to five per decade and the cost cap be increased to $500M per mission (from $425M for the mission to be selected this summer).  This year’s fiscal year 2013 budget proposal, however, proposes cutting the overall budget for NASA’s planetary with reductions to the Discovery and New Frontiers missions in the out years to refund the Mars program.  (See this post on the proposed budget.  Current budget plans provide full funding for the recently selected New Frontiers OSIRIS-REx asteroid sample return mission and the Discovery mission to be selected this summer.  Budgets for these programs are then reduced as funding for Mars missions increases, impacting the pace of future mission selection.) 

Along with the description of the current candidate missions, Nature also discusses its assessment of the implications of rising mission complexity and costs:  “The growing lag — and the escalating costs and complexity that have caused it — is having a deleterious effect on the programme, some NASA observers say, because it creates an increasingly risk-averse approach to mission selection...  All of this is why Gregg Vane, the programme manager for mission formulation at NASA’s Jet Propulsion Laboratory in Pasadena, California, says that Discovery has strayed from its original intended purpose, which was to be a riskier counterpoint to the too-big-to-fail flagships. Failure is no longer an option for a Discovery mission either, he says. ‘The tolerance for risk is significantly lower than it has been in the past.’”  NASA disputes this assessment: "Jim Green, director of NASA’s planetary-science division, flatly denies this charge. 'What is it about those [missions] that you think is averting risk?” he asked. “You can’t tell me that the missions we’ve executed in Discovery are not pushing the envelope.'"

Editorial Thoughts: NASA’s managers seemed trapped between a rock, the easy low complexity compelling planetary missions have been done, and a hard place, tightening budgets.  Whichever of the three current candidate missions is selected, it will provide compelling science.  I presume that the next set of candidate missions will be equally compelling.  Within its constraints, NASA’s managers are finding exciting missions.  (I have no way to assess whether or not, as Nature claims, the program is becoming more risk adverse.)

Any relief from this situation will have to come from the political process.  Adding an average of $75M per year to the Discovery program should allow a third mission per decade.  (The costs quoted above are for the Principle Investigator costs; NASA has additional costs on top of the PI costs such as launch costs and management costs.  I’ve never seen a full accounting of Discovery mission costs, but my back of the envelope calculations suggest $750M may be right.)  The House of Representative’s proposed FY13 budget would increase next year’s budget for the Discovery and New Frontiers programs by$115M.  (The Senate’s proposed budget would not increase either budget.)  While the Nature article discusses the problems of the Discovery program (budget cap currently at $425M) the New Frontiers program (budget cap currently at ~$800M) seems to face similar problems.

The Discovery program has been a phenomenal success.  I believe it deserves additional funding to increase the pace of missions in the coming decade.

Thursday, July 5, 2012

Mars Concepts and Approaches - Aerial Concepts

If you are an ecologist, as I am, summer is likely to be your busy season.  Phil Horzempa, who wrote the last post also, is kindly helping to fill the gap.  With this post, Phil continues to look at the ideas presented at the Mars Concepts and Approaches Workshop with an emphasis on concepts for aerial missions.  - VRK

Aerial Mobility and MPPG Strategy

The Mars Concepts workshop was a feast for those interested in exploring the Red Planet.There were numerous suggestions for ways to get around on Mars. In today’s post, I will focus on one sector - aerial mobility.

Balloons and airplanes were once touted as a way to obtain very detailed visual images. However, proposals such as the MAGIC ultra-high-resolution camera (1) promise to produce images from a Mars orbiter that would make those systems obsolete. Multi-spectral imaging systems with much higher resolution than the CRISM spectrometer onboard the MRO are also being planned. Therefore, those who propose aerial systems have found new uses for them.

One suitable task for an aerial platform would be to visit, up-close, more sites than could a rover.Another advantage of aerial vehicles is the ability to get to sites that are inaccessible to rovers, such as recurrent gullies on crater rims. High-resolution, non-visual, non-infrared, remote sensing is yet another. This would include searching for underground ice or methane seeps, or high-resolution mapping of remanent magnetism in Mars' ancient crust. In addition, with NASA now seeking synergy between manned and unmanned Mars programs, the proposals often make a nod toward their usefulness in obtaining precursor data.

There were proposals for balloons and airplanes at this meeting.However, this worksop also featured presentations for aerial systems that are quite innovative. Let's begin with a few of those concepts.

The first category includes Mars hoppers. This concept envisions a lander that is able to make substantial hops from place to place on Mars. This allows rover-class investigations to be conducted at widely separated locations. One hopper proposal, by Moeller (2), could travel approximately 70 km per hop. It would use radioisotope energy to run an in-situ resource unit (ISRU) device to generate CO2 and O2. The CO2 is then "burned" as rocket fuel for its thrusters. It takes a hop about every 200 days.A rather able, yet complex design.

Also in this category are hoppers that use compressed CO2. One of these is Robert Zubrin's Gashopper vehicle (3). This design is simplicity itself, as far as its fuel supply. It would use compressed Martian air (essentially pure CO2) and use it as thruster "propellant." Elegant in design, with no combustion chamber required. The Gashopper's fuel supply would be unlimited - the atmosphere of Mars. The CO2 is stored as a liquid at 10 Bar pressure, with no cryogenic storage and handling required. As Zubrin pointed out, CO2 is a poor rocket propellant, but it is readily available. To produce thrust, the CO2 is passed over a 1,000K pellet bed. At 80 lb. of thrust each, the thrusters can propel the Gashopper to a distance of 20 miles, if it is a simple lander. However, with wings, each "hop" can be up to several hundred kilometers. In this concept, the Hopper could carry a mini-rover which would investigate each landing site for about a month, while the Hopper was replenishing its CO2 supply. The Hopper itself could carry a Ground Penetrating Radar, GPR, to search for underground ice deposits. (Figure 1)

Figure 1

Another example is the ASRG Geyser Hopper (4) which uses hydrazine pulsed thrusters. The advantage in this concept is the use of proven technology. This model of thruster was thoroughly tested for the Phoenix lander, and performed splendidly.

The next proposal in this category was a combination mission - hopper and entomopter (5). The hopper in this proposal mimics the jump mechanics of a frog. It will have 4 legs, with the knee joints powered by a pneumatic artificial muscle system. The muscles will use compressed CO2 drawn from the Martian atmosphere. A typical jump will travel 300 meters horizontally, with a maximum altitude of 150 meters. A proposed mission for this hopper would investigate the Arsia Mons system of lava tubes/skylights in the Tharsis region of Mars. (Figure 2) The hopper would position itself close to one of the skylights, then launch an entomopter to investigate the interior. An example of one of these bug-like robots was covered in my earlier post.

Figure 2

There were several balloon proposals. Their advantages include being able to conduct aerial reconnaissance for weeks/months (as opposed to short-duration planes), and needing no power to generate lift. These vehicles can perform remote-sensing with higher fidelity than an orbiter. One example was the PICCARD Discovery proposal. It had a 2-kg. payload, including magnetometer and camera, and used an 11.5-meter diameter balloon. A beef-upped version of this mission would include a 10-kg. high-resolution subsurface radar mapper

One of the more interesting entries in this category was a hybrid balloon/kite (6). The LArK mission would be targeted to investigate the skylights in the Tharsis volcanic province. Figure 3. The LArK system would include a science module that could be winched down to investigate a skylight and/or lava tube, as the kite structure hovered overhead. Figure 4. One advantage of this mission is that it makes this volcanic region accessible to researchers. The Tharsis plateau is at an average altitude of 5 km., and is thus is off-limits to currently developed technologies for landing on Mars which need lower elevations for the parachutes to slow the lander sufficiently.

Figure 3

Figure 4

The gullies on Mars have generated a lot of interest, but like the lava tube skylights, they are inherently difficult to investigate. One approach to reaching them would be to use an electric helicopter. This proposal (7) would target the gullies, or RSL's (Recurring Slope Lineae), that extend for many meters down the slopes of Martian crater rims. Their origin is mysterious, perhaps caused by liquid water, or other mechanisms, such as dry flow, as has been seen on the Moon by the LRO. They are accessible from air, but could be impossible for a rover to reach. This helicopter would hop from safe spot to safe spot until it was within reach of an RSL.The NRL's (Naval Research Laboratory) SPIDER electric unmanned helicopter can be considered to be a prototype.

One of the more unusual entries in the aerial mobility theme is the Mars Cannon Assisted Flying Exploration, or CAFE mission (8) would launch small aircraft to swarm over a specific region, such as a canyon. Figure 5. The aircraft are packaged in ballistic shells that are launched using compressed CO2. Here is yet another use of this simple ISRU method.

Figure 5

Regarding overall strategy, the Mars Program Planning Group, MPPG, has issued an update that is fascinating and revealing. Reading the tea leaves of this report (9), I am guessing that a likely scenario would see Mars Sample Return take place at a reduced tempo. In fact, one exploration pathway option in this report would see samples cached and placed into Mars orbit by the late 2020's or early 2030's. The report states that samples orbiting Mars, No Later Than 2033, for return to Earth by humans and/or robotic missions, is a point of possible convergence for the parties involved. It is fascinating to see how NASA's manned sector may now dovetail with the decades-long effort to return samples from Mars.If this becomes the adopted exploration roadmap, then NASA's unmanned science directorate need only worry about caching samples and getting them as far as Mars orbit. The astronauts will take care of the rest. This could be a major budget relief for NASA's solar system exploration program.
 This document indicates that NASA's budget cannot support a Rover mission in 2018. It seems that an orbiter for that launch window is preferred for several reasons. There is the budget restriction, but also a dire need for an orbital relay for present, and future, surface missions. As the recent extended safe-mode for the 2001 Mars Orbiter shows, existing orbital assets are aging. In addition, even though the MAVEN Mars Orbiter will carry a relay radio link, its elliptical orbit will mean that it will be within range of landed missions on a limited basis. Rover missions require daily relay links in order to conduct a useful mission. Assuming a MER-like lifetime, the MSL Rover should still be operating in 2018. In addition, the ESA/Roscosmos Exomars rover should land that year, and may need orbital relay services. Beyond that are any future NASA rovers or other surface missions. This document indicates that the budget may support a rover mission in 2020.

This report lists various "drivers" for future Mars missions. Science is the top priority. However, another top priority is the degree to which the program advances knowledge and capabilities required for manned flight in the 2030's. This "marriage" may benefit both programs. The unmanned missions, being tied to a long-range goal of human exploration of Mars, may have access to a larger pool of funds. At the same time, the manned program will have the data that it needs to realistically plan missions. Also, with samples of Mars rocks waiting in orbit, there is an added incentive to get astronauts out to the red planet.

Philip Horzempa
- - - -


1. "Mars Geoscience Imaging at Centimeter-Scale (MAGIC) from Orbit"
 by Malin Space Science Systems

2. "Mars Hopper for LongRange Mobility, Regional Surface and Lower Atmospheric Investigations, and In-Situ Resource Utilization" by Moeller et al

3."The Mars Gashopper" by R. Zubrin

4. "ASRG Mars Geyser Hopper" by G. Landis et al

5. "Hopper/Entomopter Tandem System for Surface and Subsurface Exploration of Mars"
by Gemmer et al

6. "Mars Aerial and Subsurface Exploration Using the LArK (Lighter Than Air Kite) Concept"
by L.E. Edwin et al.

7. "Vertical Takeoff and Landing UAV's for Exploration of Recurring Hyrological Events"
 by Lemke et al

8. "Mars Cannon Assisted Flying Exploration (CAFE)
 by J.D. Denhar et al

9. NRC Committee on Astrobiology and Planetary Sciences (CAPS) Report of May 23, 2012