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Register a new userProspect for UV observations from the Moon. III. Assembly and ground calibration of Lunar Ultraviolet Cosmic Imager (LUCI)
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The Lunar Ultraviolet Cosmic Imager (LUCI) is a near-ultraviolet (NUV) telescope with all-spherical mirrors, designed and built to fly as a scientific payload on a lunar mission with Team Indus - the original Indian entry to the Google Lunar X-Prize. Observations from the Moon provide a unique opportunity of a stable platform with an unobstructed view of the space at all wavelengths due to the absence of atmosphere and ionosphere. LUCI is an 80 mm aperture telescope, with a field of view of 27.6x 20.4 and a spatial resolution of 5, will scan the sky in the NUV (200-320 nm) domain to look for transient sources. We describe here the assembly, alignment, and calibration of the complete instrument. LUCI is now in storage in a class 1000 clean room and will be delivered to our flight partner in readiness for flight.
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Space astronomy in the last 40 years has largely been done from spacecraft in low Earth orbit (LEO) for which the technology is proven and delivery mechanisms are readily available. However, new opportunities are arising with the surge in commercial aerospace missions. We describe here one such possibility: deploying a small instrument on the Moon. This can be accomplished by flying onboard the Indian entry to the Google Lunar X PRIZE competition, Team Indus mission, which is expected to deliver a nearly 30 kgs of payloads to the Moon, with a rover as its primary payload. We propose to mount a wide-field far-UV (130--180 nm) imaging telescope as a payload on the Team Indus lander. Our baseline operation is a fixed zenith pointing but with the option of a mechanism to allow observations of different attitudes. Pointing towards intermediate ecliptic latitude (50 deg or above) ensures that the Sun is at least 40 deg off the line of sight at all times. In this position, the telescope can cover higher galactic latitudes as well as parts of Galactic plane. The scientific objectives of such a prospective are delineated and discussed.
This paper reviews improved calibration methods for the Lunar Reconnaissance Orbiter Lunar Exploration Neutron Detector. We cross calibrated the set of LEND observations and models of its detectors physical geometry and composition against the McKinney Apollo 17 era measured neutron flux, Lunar Prospector Neutron Spectrometer epithermal neutron observations, Earth based Galactic Cosmic Ray observations and altitude dependent models of the Moon neutron emission flux. Our neutron transport modeling of the LEND system with the Geant4 software package allows us to fully decompose the varying contributions of lunar, spacecraft and instrument dependent sources of neutrons and charged particles during the LEND mission. With this improved calibration, we can now fully predict every observation from the eight helium 3 detectors and the expected total and partial count rates of neutrons and charged particles for the entirety of LEND now ten plus year observation campaign at the Moon. The study has resulted in an improved calibration for all detectors. The high spatial resolution of LEND collimated and uncollimated sensors are illustrated using the neutron suppression region associated with the south polar Cabeus permanent shadowed region.
We reported the photometric calibration of Lunar-based Ultraviolet telescope (LUT), the first robotic astronomical telescope working on the lunar surface, for its first six months of operation on the lunar surface. Two spectral datasets (set A and B) from near-ultraviolet (NUV) to optical band were constructed for 44 International Ultraviolet Explorer (IUE) standards, because of the LUTs relatively wide wavelength coverage. Set A were obtained by extrapolating the IUE NUV spectra ($lambda<3200AA$) to optical band basing upon the theoretical spectra of stellar atmosphere models. Set B were exactly the theoretical spectra from 2000AA to 8000AA extracted from the same model grid. In total, seven standards have been observed in 15 observational runs until May 2014. The calibration results show that the photometric performance of LUT is highly stable in its first six months of operation. The magnitude zero points obtained from the two spectral datasets are also consistent with each other, i.e., $mathrm{zp=17.54pm0.09}$mag (set A) and $mathrm{zp=17.52pm0.07}$mag (set B).
The Lunar Cherenkov technique is a promising method for UHE neutrino and cosmic ray detection which aims to detect nanosecond radio pulses produced during particle interactions in the Lunar regolith. For low frequency experiments, such as NuMoon, the frequency dependent dispersive effect of the ionosphere is an important experimental concern as it reduces the pulse amplitude and subsequent chances of detection. We are continuing to investigate a new method to calibrate the dispersive effect of the ionosphere on lunar Cherenkov pulses via Faraday rotation measurements of the Moons polarised emission combined with geomagnetic field models. We also extend this work to include radio imaging of the Lunar surface, which provides information on the physical and chemical properties of the lunar surface that may affect experimental strategies for the lunar Cherenkov technique.
MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes (IACT) that observe Very High Energy (VHE) gamma ray sources. The PMTs in their cameras are designed to operate under moonlight, but they are limited to Moon phases below 93% (300 Moon hours per year), as they can get damaged if the amount of light they receive is too high. As a result, they cannot be used in the three to five nights around full Moon. We have selected commercial inexpensive UV-pass filters rejecting light above a wavelength of 420 nm, where the moonlight intensity is stronger. We mounted them on light-weight frames that can be easily installed on the telescope cameras. Test observations have been performed during the last nine months, from which a moonlight transmission of about 20% and a Cherenkov light transmission of about 45% are estimated. This allows the observation of sources down to an angular distance of 5 degrees to the Moon during Full Moon: essentially in the whole sky and all possible moonlight conditions. Therefore, the duty cycle of MAGIC can be extended by about 30%, including nights when VHE observations with IACTs are currently not feasible. Here we evaluate the preliminary performance, in terms of sensitivity and energy threshold, of the MAGIC telescopes equipped with the UV-pass filters under different moonlight intensities, as inferred from Crab Nebula observations and Monte Carlo simulations.
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