Spectroscopic Analysis of Asteroids
That would produce a lot of outgassing because you are heating a carbonaceous material?
Gary Hughes
UC Santa Barbara
Photonic Propulsion for interstellar missions
Notes by Paul Fischer
Challenges what we can do with a laser in space
Laser array powered by Photovoltaics could be used to heat an asteroid at 10 MW per square meter
Creates melting and evaporation and ablation of substrate
Thermal radiation from the heated spot
Atomic and molecular absorption in ejected plume
Spectrometric detection can then occur to determine the composition of the asteroid
Called: Remote Laser Evaporative Molecular Absorption (R-LEMA) Spectroscopy
Laser Induced Breakdown Spectroscopy (LIBS) as comparative method
Mars Science Laboratory ROver
“Chem Cam”
Differences:
- Pulsed Laser
- More energy, 10 TW/ m2, max distance, 8m
- Molecular dissociation, ionization -> plasma
- Optical Emission (atomic Spectroscopy) ???
Laser Induced Thermal Emission (LITE) Spectroscopy
Deep Impact Mission
Comet Tempel 1
Observed from Spitzer
Space Telescope
- Surface Impactor: 364 kg
- Particle Emission from Impact ~10^6kg of ~10um particles
- Mid-, Long-Wave IR Emission Spectroscopy from Spitzer Space Telescope (from ~.75 AU) determines emissions of materials and do molecular composition
What we envision is Molecular Absorption spectroscopy (gas phase)
Why R-LEMA?
The mission scenario is to Asteroid 2014 HM187
Its orbit does not cross earth, but does cross orbit of Mars
Between 139 to 312 m
No former spectra exists
Why choose this asteroid?
It is in a central ring of the asteroid belt
Methane, titanium, or water? What is in the asteroid, we propose going to figure out by probing it directly
The main objective is to determine the objective with a resources assay, could be a stopping place to go to Mars as an auxiliary capability (orbital outpost positioning)
An alternative idea could be to evaluate cost of moving the asteroid into a new orbit
What if Jeff Bezos wants to expand his empire into space? Amazon Asteroid
Short discussion of Orbit Alterationa s 2ndary otpion
10 MW/m2 -> 100 uN/W
-> Mars close approaches, could create a “keyhole” with the same tech.
Back to the Arlema system for spectropscopy analysis
About 10 km view of interaction, so we modeled the asteroid, and you can see that the temperature stabilized at 21k Kelvins, making a perfect background to do IR spectroscopy, this seems to suggest that the system has a good chance of working, at the end of phase 1, we made a strong argument that we had reached phase 2, with a strong chance of working
So what to do in Phase II?
We want to test the Spectrometer in the laboratory
Target must be put into a vacuum to simulate a space environment, we had to build all of the components, the laser enters through window and heats the substrate, creating a backlight for the spectrometer view
Based on a Brueger vortex 80 design for a couple of reasons, the vertex 80 has an external port allowing such remote designs
The distance in the laboratory of 1 meter would be expanded in space
Heating things up with a laser is not like an incandescent lightbulb, the heat bounces around everywhere and these 84 hour experiments allow photodiode feedback, which is fed back into the vortex 80, and corrects for any fast changes in backlight
System Validation
Provided by a measured spectra, will be different from a system spectra
We will measure our spectra and compare it to a reference or predicted spectra
NIST has a chemistry webbook with many spectra, but the reference was difficult to find, ECOSTRESS discusses rocky materials including salt that allow the reflectance spectra and seeing what gets reflected, we hope to see some of the same absorption lines, but we need more gasphase rocky material spectra
Where to go from here? Everything in the lab seems to suggest that this will work.
Well if it works in the laboratory, we can make an argument for reaching TRL 3
We need to do something in a relevant environment, propose a formation fliying CueSat Experiment
Two CubeSts in a low orbit environment
One will be equipped with the laser, and the other with rocky material so we can prove the idea will be functional with deployment
We have already asked the Federal University at Santa Cadarino
In stage II of the NIAC process, we hope to…
At TRL3 we will propose to PICASSO of NASA
That will allow it to hit TRL4 for the Matisse Program
Is there some overlap with other ideas?
Right I think there is some room for integrated resource utilization, if other groups get there, we will be able to send CubeSats to asteroids very efficiently\
How does the vacuum replicate the plume that is expected space?
We calculate that 90% of the absorption occurs within on spot radius, most of the stuff comes off very rapidly, and needs to be quite close to the asteroids
Is the laser big enough, how do you get to that power
The laser is a collimated beam, so that is how you get to your maximal watts
Phil Lubens and the mission context for the NIAC, gives a 2 meter array, with a 10km beam, it would be 1cm in diameter
What is the total power of the beam?
The system would be 2 KW
That would produce a lot of outgassing because you are heating a carbonaceous material?
Right, we see that in the lab, all sorts of things coming off, so we focus on this small spot and what is going on below.
Our need to prospect before we arrive, we take an economic view of the problem, we have studied the problem very seriously, we have looked at mapping asteroid spectroscopy, and we think we can do it with just a few colors, involving a strategy, where we through out ambiguous cases. We do not want to arrive at an asteroid and not have water there. The first generation we avoid such asteroids. If you have to fly to the asteroid to find what it is made of, you have already lost the battle. Prospecting missions can take 20 years, so we need to remotely survey these.
187 by the way does launches to Mars
What Delta V?
3 meters per second
What is the somatic period
About…
Spot on the surface or wavelength?
We envision using monochromatic laser for power to heat the asteroid.
But you need a reference spectrum?
Right, to validate the approach, once the data is acquired.
That is something that has already been validated, but we have not been able to find a reliable reference spectrum.
Do mining or drilling companies have access to these records?
This sort of information is proprietary and more difficult to get in public databases.
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