Instruments of HOSERLab:
1. Field portable instruments
2. Lab bench instruments
3. Microspectrometers
4. Other instruments
Central to our efforts to develop Inukshuk and ensure that its scientific instruments will perform as expected, are our Mars environment chambers. In support of Inukshuk we have constructed two environment chambers that we use to simulate the surface conditions on Mars. 
The first is “mini-ME” (mini-Mars Environment). Mini-ME is about the size of a large coffee travel mug. Inside mini-ME we can place a sample (or multiple sample holder) that is up to 40 millimetres across and 10 millimetres thick. Mini-ME is connected to a supply of dry carbon dioxide on one side (the inlet port) and a vacuum pump on the other side (outlet port). By adjusting valves that balance the flow of carbon dioxide into the chamber against the pull of the vacuum pump we can set the atmospheric pressure to whatever value we want (as low as 0.1% of Mars surface pressure or 0.0001% of Earth’s atmospheric pressure at sea level) and maintain a flow of carbon dioxide so that any gases that come off the sample are swept away.
The larger environment chamber is big-ME. Big-Me measures 100 x 100 x 70 centimetres in size, or about the size of a two drawer filing cabinet tipped on its side. Big-ME is also capable of holding pressures as low as, or lower than, are present on the surface of Mars. Th
e larger volume of big-ME means that we can use it to look at the stability of bigger samples, or to test the performance of scientific instruments or parts of Inukshuk under Martian surface conditions.
Both mini-ME and big-ME are outfitted with interchangeable windows made of sapphire, polycarbonate, silica glass, and zinc selenide. These windows allow us to watch the samples while they are in the chambers, as well as to measure their spectral properties whenever we want. Some of the more technical details concerning the environment chambers are provided in the attached abstract from a recent Lunar and Planetary Science Conference.
HOSERLab is the name we have given to our overall laboratory facility where we conduct experiments to support the development of the Inukshuk mission. HOSERLab (which stands for Hyperspectral Optical Sensing for Extraterrestrial Reconnaissance Laboratory) has been equipped with a number of scientific instruments that we can use in conjunction with mini-ME and big-ME. The scientific instruments that are central to HOSERLab are called optical spectrometers, and it is worth discussion what optical spectroscopy is before getting into a more detailed description of HOSERLab.
What is optical spectroscopy?
Optical spectroscopy, in its most general sense, is a technique for measuring how some materials (let’s call it a target) interact with light. For this discussion, let’s say that our light source is the sun. To understand a bit about spectroscopy, it’s necessary to delve into a bit of physics (but just a bit).
Sunlight consists of photons, which can be thought of as little packets of electromagnetic energy. The sun emits photons of all different energies. The photons that we can see are termed “visible light”, but the sun also emits photons with energies that we cannot see. To convince yourself that sunlight consists of photons with different energies, have a look at a rainbow or see what happens when you pass sunlight through a prism. In both cases you see a range of colours: violet, blue, green, yellow, orange, red. Each of these colours corresponds to photons with specific energies. Our eyes are able to distinguish photons of different energies that our brain then interprets as different colours.
As you scan across a rainbow, the photons with the highest energies that we can see are interpreted by our visual system to appear as violet. The photons that have energies that are higher than what we can see (with energies higher than “violet”) are called ultraviolet photons (literally “higher than violet”), and we know that the sun puts out these “invisible” photons because even though we can’t see them, our skin is sensitive to ultraviolet photons. Ultraviolet photons can interact with our skin, causing us to tan, so even though we can’t “see” ultraviolet photons, the way our skin darkens in sunlight is evidence that they exist, and you could say that our skin “sees” ultraviolet photons.
At the other end of the spectrum, the photons with the lowest energies that our eyes can see are interpreted by our visual system to appear as red. Once again, the sun also puts out photons that have energies that are less than the energies of visible photons (with energies lower than “red”). These photons are termed infrared photons (literally “lower than red”). Once again, we cannot see infrared photons but we can detect their presence. The best example of infrared photons is heat lamps that are used in restaurants. Heat lamps have a dull red glow to them, but most of their energy consists of invisible infrared photons. Our skin is sensitive to infrared photons, because when you place your hand under a heat lamp, you can feel it warm up. Our skin is sensitive to the presence of infrared photons, which we sense as heat.
Now that we’ve shown that sunlight consists of photons with a range of energies, and that our eyes can only see photons that have the right energies (those that fall in a limited range), so what? It turns out that different targets absorb photons in different ways depending on what the target is made of. Leaves appear green because the compounds, like chlorophyll, that make up leaves are good at absorbing photons with energies that correspond to violet, blue, yellow, orange, and red, but not so good at absorbing photons with energies that correspond to green. As a result, photons that have energies that correspond to green, get scattered by cells in the leaves and some photons are reflected back at our eyes so that we can see them, while photons with other energies that we might be able to see are more efficiently absorbed by leaves.
Sunlight that strikes a target can interact with the target in two main ways. The first is that a photon might be reflected by a target and not interact with it at all (a mirror is very good at reflecting photons so they don’t interact with a target). The second way that a photon could interact with a target is by its being absorbed. Things that are black appear black because they are very good at absorbing photons with energies that span the visible spectrum.
If we could somehow “see” a target by how it interacts with ultraviolet and infrared photons, we would do a better job of distinguishing different materials. Think about how much more informative a colour picture is than a black and white picture. Lots of things (and colours) look the same (a medium shade of gray) in a black and white photograph, whereas we can tell more things apart in a colour photograph. If we could extend this concept, that you can more things apart if you see in colour versus black and white, to the ultraviolet and infrared spectral regions, we would be able to, conceptually, do an even better job of telling different materials apart.
Fortunately, even though we can’t see in the ultraviolet and infrared, we can build instruments (spectrometers) that can. It turns out that the infrared region is more useful than the ultraviolet for discriminating different targets (for reasons that aren’t worth losing sleep over). By including how infrared light interacts with a target in our analysis (in addition or in place of visible light) in essence what we are doing is looking at a target with increasing “colours” and we can start to tell apart targets that are only subtly different from each other. Again, go back to the concept of how a colour photograph provides better ability to tell things apart than a black and white photograph; we are extending this to what we call “hyperspectral” (I also like to think of it as “supercolour”).
Now, let’s come back to HOSERLab’s spectrometers. We can express photon energies in units of energy (using units such as wavenumber or frequency) or in the more familiar notation of wavelength (using units such as nanometers, Angstroms, or microns). Planetary scientists usually work in units of “microns” or micrometres (millionths of a metre). Visible light (the light that our eyes can see) has wavelengths of between about 0.4 and 0.7 microns (or 400 and 700 nanometres (billionths of a metre)). Across this narrow range of wavelengths, we can tell many targets apart (e.g., green healthy leaves versus brown unhealthy leaves, etc).
The infrared spectrometer that will be used on Inukshuk will have a wavelength range sensitivity from about 800 to 4000 nanometres. This is about 10 times the range of the human eye! As a result, our spectrometer will, in one sense, be much more capable than the human eye of telling one target from another.
Instruments of HOSERLab:
HOSERLab’s spectrometers are divided into three categories: (1) those that are field portable and can be used to look at samples in min-ME and big-ME; (2) those that stay in the laboratory and are used to study samples in terrestrial conditions; and (3) those that are used to look at samples in a microscopic mode. The specifications of the various instruments are described in the attached abstract from Cloutis et al. that summarizes the capabilities of HOSERLab as presented at the 2006 Lunar and Planetary Science Conference.
Here we get into technical details a little bit to describe the specific capabilities of HOSERLab’s suite of spectrometers.
1. Field portable instruments
HOSERLab’s stable of field-portable spectrometers is made up of 3 separate instruments. The first is an ultraviolet-visible S2000 spectrometer from Ocean Optics. This instrument measures target spectra from 200 to 1150 nanometres with a spectral resolution of less than 1 nanometre. This instrument has been used to look at the ultraviolet spectra of various minerals that may be present on the Moon and Mars, as well as to search for very narrow absorption bands in various candidate minerals that may be used for unique mineral identification. The Ocean Optics instrument is equipped with fibre optic cables so that samples can be looked at in various configurations.
The second field-portable instrument is a FieldSpec Pro HR spectrometer from Analytical Spectral Devices (ASD). This instrument is also equipped with a fibre optic bundle to measure targets in various configurations(including through the sapphire windows of mini-ME and big-ME. This instrument covers a wider wavelength range than the Ocean Optics instrument (400-2500 nanometres) but with coarser spectral resolution (between 2 and 7 nanometres).
The third field portable instrument is a Model 102F Fourier transform spectrometer from Designs and Prototypes. This instrument covers the wavelength range from 2 to 16 microns with 6 wavenumber resolution
When we get into the infrared region, we generally switch conventions from nanometers to microns or wavenumbers. To convert from one to the other is fairly straightforward. To convert from microns to nanometers, divide microns by 1000 to get nanometers. To convert from microns to wavenumber, divide microns into 10,000 (and vice versa to go from wavenumber to microns). Thus, 1000 nanometres is equal to 1 micron, which is equal to 10,000 wavenumber. Similarly 2000 nanometres is equal to 2 microns, which is equal to 5,000 wavenumber.
2. Lab bench instruments:
HOSERLab is equipped with 3 main lab bench spectrometers. Lab bench spectrometers are generally larger than field-portable instruments, are generally more capable, and can only run off wall power (our field portable instruments can run off wall or battery power).
The first lab bench spectrometer is a Model 570 instrument from Jasco. This instrument covers the wavelength range from 190 to 2500 nanometres, with sub-nanometre resolution. It can be used to measure reflectance or transmittance spectra. It covers the same wavelength range as the ASD field-portable instrument, but with higher spectral resolution.
The second lab bench instrument is a model M500 spectrometer from Buck Scientific. This spectrometer covers the wavelength range from 2 to 16 microns (like our Designs and Prototypes field-portable instrument. It can also measure reflectance or transmittance spectra of samples. Its spectral resolution is higher than that of the Designs and Prototypes instrument.
The third lab bench instrument is also the most capable. It is a model Vertex 70 Fourier transform spectrometer from Bruker Optics that has been custom configured for our specific applications. It covers the wavelength range from 0.4 to 200 microns with 1 wavenumber spectral resolution. It can be used to measure reflectance or transmittance spectra of samples.
3. Microspectrometers:
We have found occasions when it is useful to measure very small spots on samples or to look at powdered samples on a grain-by-grain basis. For this, we have a Hyperion 2000 system from Bruker Optics. This instrument covers the range from 0.4 to 16 microns and also has 1 wavenumber spectral resolution.
4. Other instruments:
HOSERLab is also equipped with other instruments that complement our optical spectrometers. These include the following:
two Raman spectrometers from Delta Nu that cover the wavelength range from 3400 to 200 wavenumber. Raman spectroscopy is complementary to optical spectroscopy because it responds to different target properties.
a Model 1110 elemental analyzer from CE instruments. This elemental analyzer is used to measure the abundances of light elements (specifically carbon, nitrogen, sulfur, and hydrogen) in our samples.
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