Saptarshi Bandyopadhyay
Lunar CraterRadio Telescope (LXRT) on the far side of the moon
Notes by Paul Fischer
Showing with wavelengths are colored 10-100m wavelength band that is 3-30 MHz radio frequency band
Isolation of LCRT from earths noise wavelengths greater than 10 MHz have not been explored by humans, this telescope will measure 3-30MHz
The Moon provides shedding against noise from earth, hence far side
This will be the largest filled aperture telescope in the solar system
The idea has been around since the 1950s
Lunar Arecibo type …
Technical challenges section of lunar craters…
Selection.
Aricebo type
…
…
Selection of image by royal society
1km diameter deployable reflector
Side view of the concept
Philosophical transactions of the royal society…
Hubble looks at the midrange, there is no data on the nature of the cosmic dark ages, this telescope will fill the gap
Nobel prizes on cosmetology - improves on former cosmelogical models
Spatial structure and fluctuations of the redshifted hyperfine transition of hydrogen, like teen meters or more spectral shape and polarization needed to extract the signal are all known
Going towards the left on this plot are supposed to arrive the dotted line is the best astro-free theoretical model, different models have been proposed
This will collect data from the dark ages
This is 5 times greater than the signal used to extract the foreground signal galactic with altitudes on the moon
This cable shows ….
Lunar crater selection there are over 82k craters in just 3-5 km diameter range that are appropriate
We chose the cradter at 9…x169…
Selector wire mesh design is stronger and may be lifted due to low gravity
The spacing must be less than min theta over 4
Variable mass concepts where linear density of cosin … x/ pocosin x
Parabolic mesh equation spans six orders of magnitude, the computational challenge of designing such a mess is tough
Four interdisciplinary constraints:
Structural and thermal analysis - prove loads and temp data can be survived
Deployment from stored configuration
Radio frequency performance
Launch mass and launch loads
Current work: design reflector that simultaneously satisfies constraints
The gravity and thermal loads are mapped
The change in temperature in the night is only 10K
We chose 16 lift wires …and 4 lift wires…
Next we focus on the RF performance, from 13 MHz …
Understanding the three docs is important
Performance of the periodic antenna will be improved in phase two
Concept of operations
Earth to moon, landing on moon, antenna prep, deployment, data collection….
Three options on the right CONOPS trade space so the decision to use rovers or robots, increased rovers reduces construction time, and the times depend on lighting, terrain and loads
Packaging of reflector
Deploy lift wires
Anchor
Lift and deploy mesh
We went thorugh different options
Quasi static deployment
Final free deployment, each can be used effectively
The wire mesh would be a suitable lunar crater
Q: mechanical challenges to the deployment of the system as a whole? Rovers going out and tension for the cable as a whole, what sort of delivery system will we be looking at?
A: combined masses of 5-6 metric tons, we are keeping an eye out on starship, this has the capability of taking a hundred metric ton payload and this is something we will actively investigate in phase ii
Q: can the parabolic method work in the visible regime?
A: theoretically yes, but you need increased magnification and in practice this would never be useable.
Q: can you talk more about the science objectives here?
A: the neutral hydrogen at 21 cm release of photons, and that has been released say 13 billion years ago, this increases all the way to 10 meters or more. Why are we trying to observe? We really don’t understand dark energy and dark matter, and the rest is all dark energy and dark matter. There should have been more antimatter, and suddenly it vanished, there are lots of cosmological concepts, and we want to collect data that would throw a light at these questions, we would be able to understand these energy changes in our human society, think of a hundred years ago
Q: general speaking about the advantages of a lunar telescope as oppose to one on earth. The ionosphere blocks these wavelengths and you could potentially put something back on earth and potentially override that over super long periods of time. Even if you want to put something on our topic, with hundreds of meters scale, that is why earth is really not a good idea. The lunar far side is a great place. Everyone wants to put something on the lunar surface, we would need additional shielding… for most of the orbit there would be exposure to radiation noise from earth. We want to make sure that our research answers one of the big unknowns, but we have remaining questions
Q:what about a rover instead of harpoons or driving through the crater itself?
A: we did not invest in different robot designs, because we already have two miracles in function.
Q: how does the thermal cycle affect the lunar cycle?
A: you do not want the change of the temperature to affect the telescope.
Q: acknowledgements
A: lots of good astronomers on the team
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