Tuesday, 18 April 2023
This talk includes the details of Chandrayaan-2 Optical payloads responsible for DEM generation of Lunar surface, DEM generation principles, methodology and results obtained so far.
The surface composition of the Moon is key to understanding it's thermal and magmatic evolution. It is also important in the context of exploration and future presence of humans on the Moon. Under the low illumination conditions, the polar regions are challenging to image. I will talk about efforts on high latitude and near polar elemental abundances measured from Chandrayaan 2.
Visible/Near Infrared (VNIR) spectroscopy is one of the most cost effective and easily available tools for remote compositional assessment of planetary bodies. Here I will be discussing about the salient results obtained from Chandrayaan-1 and contemporary lunar missions in understanding the lunar crustal composition and the presence of wide-spread hydration with special reference to the lunar poles.
Radar is a powerful tool for studying planetary geology because it is sensitive to composition, structure, and its ability to penetrate some materials to reveal buried terrain. In this talk, I will briefly present about the radar exploration of lunar poles, starting with the state of the art radar techniques involved in characterising water ice. I will discuss about the timeline of radar analyses of the lunar poles starting with earlier ground based observations to the current orbital missions.
In close cooperation with international partners, the European Space Agency (ESA) has developed a program for the exploration and the scientific utilization of the Moon. The cornerstones of the ESA program will be presented together with the main milestones for the years to come.
LUPEX is the joint lunar exploration mission of ISRO and JAXA (Japan Aerospace Exploration Agency). ISRO is mainly responsible for developing a lander system, and JAXA for developing a rover system and purchasing a launch service.
One objective of the project is to obtain data on the quantity and quality of lunar water to clarify whether it can be used for future sustainable human activities. Another one is to obtain data to understand the principle of the water distribution and concentration to estimate the quantity of water across the Moon.
Several mission instruments to detect water ice will also be loaded on the rover. Representatives of them developed by ISRO are the Ground Penetrating Rader (GPR), Mid-InfraRed imaging spectrometer (MIR) and so on. Since direct measurement of water by conducting in-situ measurements will achieve the objectives, the rover has a drilling system to excavate the regolith as well as a sampling system to pick the regolith from a designated depth. A unique instrument developed by JAXA is the REsource Investigation Water Analyzer (REIWA) that is the integrated instrument of four major sensors; Lunar Thermogravimetric Analyzer (LTGA), TRIple-reflection reflecTrON(TRITON), Aquatic Detector using Optical Resonance (ADORE), and ISRO’s Sample Analysis Package, in order to obtain data on the quantity and quality of lunar water.
In this presentation, an overview of the LUPEX project, the status of the project and development activities of the rover as well as the mission instruments that JAXA develops in the basic design phase are introduced.
Seismology is the best geophysical tool to determine the internal structure of a planet. Seismometers with varying performance parameters in terms of sensitivity and bandwidth are used to conduct seismic experiments. In planetary missions, it is very important to develop low power consuming instruments with less form factor. One of the enabling technologies to achieve this goal is silicon micromachining, also called Micro Electro-Mechaincal Systems (MEMS) technology. This talk presents the first attempt by India in developing a miniature instrument for lunar seismic studies proposed to be a part of the upcoming lunar mission. The trade off considerations in the realization of the instrument and the possible modifications for future missions will also be discussed.
Wednesday, 19 April 2023
Future GW detectors like LISA and the proposed Cosmic Explorer and Einstein Telescope will herald a new era of GW science and astronomy. Together with pulsar timing arrays and inflationary probes, a frequency band spanning over 20 decades will be under observation. However, these detectors leave important gaps for GW detections, most notably the decihertz band, which would open exciting possibilities for GW cosmology, multi-messenger astronomy, and fundamental physics. In this talk, we present a new detector concept, the Lunar Gravitational-wave Antenna (LGWA), which measures vibrations of the Moon caused by GWs. The Moon is known to be several orders of magnitude quieter in terms of seismic perturbations than Earth, which is key for the realization of LGWA. It relies on a revolutionary concept for an ultra-sensitive, cryogenic vibration sensor with sub-picometer sensitivity in the decihertz band. An array of at least four seismic stations deployed in a permanently shadowed region at the lunar north or south pole serves to distinguish between GW signals and the seismic background. In this way, LGWA fully exploits the unique lunar environment and has the capability to achieve the first GW observations in the decihertz band.
At the heart of the Lunar Gravitational-wave Antenna (LGWA) are cryogenic inertial sensors with sufficient sensitivity in the decihertz band [1,2]. An array of four of these sensors will be deployed in a permanently shadowed region. The Moon is known to be several orders of magnitude quieter than Earth, and the array allows for subtraction techniques to further reduce the extremely weak seismic background predicted from meteoroid impacts and moonquakes. In this way, LGWA becomes a technologically feasible concept fully exploiting and investigating the unique lunar environment and with the capability to achieve the first gravitational-wave observations in the decihertz band. Here, I will present the current technology developments of optical and superconducting inertial sensor readout, a low-vibration sorption cooler to achieve liquid helium temperatures in the payload and further deployment details [3].
[1] JVvH (2020), JINST 15 P06034
[2] JVvH+ (2022), NIM A Vol. 1041, pp. 167231
[3] JVvH+ (2023), arXiv:2301.13685
This talk presents a compact displacement sensor that can be used to measure proof mass motion of Lunar Gravitational Wave Antenna (LGWA). The sensor consists of a fiber-based laser interferometer that uses optical resonators. In principle, such a heterodyne cavity-tracking readout scheme can reach noise levels below 10^(-16) m/rt(Hz) with reasonable cavity and readout configurations. The talk discusses the main noise contributors and how one could expect a sub-femtometer noise floor in such an opto-mechanical readout.
To use this readout for vibration measurements, one basically tracks the heterodyne frequency and retrieves the displacement information. This in turn requires a high dynamic range frequency-tracking system. Such a ‘Phasemeter’ can be realized using Field-Programmable Gate Arrays (FPGAs) with integrated RF data converters. Our progress on the development of such a ‘GHz Phasemeter’ is also presented.
The LGWA detects mid-frequency gravitational waves by observing the very weak vibration of the moon excited by the tidal force generated by gravitational waves, to meet the scientific goal of this project, the sensitivity of the vibration sensors need to be as high as 10^-15 m s^-2 Hz^-1/2 in the frequency band between 1 mHz~10 Hz. Vibration sensing based on the quantum effects of superconductor can meet this challenging sensitivity requirement with a tabletop scale system, and the permanently shadowed region on the moon where LGWA is to be deployed offers a nature cryogenic environment, making this technology a very competitive candidate for the vibration sensing. This talk will briefly introduce this technology and present some thoughts on its application on LGWA.
This presentation deals with the modeling of solar illumination and surface temperatures at the lunar poles.
Apollo seismic observations revealed that Moon is still seismically active today. However, the seismic environment is very different from Earth and the Moon. In this presentation, we will review the seismic observation made on Moon and discuss the noise environment of Moon. Moon is one of the most seismically quiet environments that we have ever explored. The biggest difference from Earth is that there is no atmosphere and ocean on the Moon. This has significant impact on the noise condition on the Moon and for example, the micro seismic peak that is ubiquitously observed on Earth will not be observed on Moon. The micro seismic peak is excited by oceanic waves and this will mask signals around 4 – 30 seconds period. Observation of that frequency band will be challenging on Earth while it will be almost noise free on Moon. Lack of atmosphere, ocean and human activity make Moon an ideal environment for gravitational wave detection. We will review the observation from Apollo to discuss our current knowledge of the noise environment of Moon. We will also discuss some perspectives for the future with possible launch opportunities that will further inform us with seismic environment of Moon and a new generation seismometer that is now under development for future seismic observations.
Following the detection of GW150914, it was soon realized that this source could have been potentially seen by LISA years before merger, opening the possibility of multiband gravitational wave astronomy. Although multiband observations with LISA and ground based detectors are possible, a deciHz band detector would be ideally placed to fulfil the promise of multiband GW astronomy. I will describe some relevant aspects of the science case for multiband GW observations and highlight the potential of LGWA in this respect.
DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a future Japanese space gravitational-wave antenna. There are many science targets that DECIGO aims at, including the detection of primordial gravitational waves, direct measurement of the acceleration of the Universe, the revelation of the formation of massive black holes, and many others. DECIGO consists of four clusters of spacecraft, and each cluster consists of three spacecraft with three Fabry-Perot Michelson interferometers. As a pathfinder/science mission of DECIGO, we plan to launch B-DECIGO to demonstrate technologies necessary for DECIGO and lead to fruitful multimessenger astronomy. B-DECIGO is a small-scale version of DECIGO with a sensitivity good enough to provide frequent detection of gravitational waves. In this talk, I will explain the aimed sciences, the mechanical and optical design, and the current status of DECIGO and B-DECIGO.
Next-generation lunar laser retroreflectors from INFN-LNF, MoonLIGHT (Moon Laser Instrumentation for General relativity/geophysics High-accuracy Tests), and from University of Maryland (USA), NGLR (Next-Generation Lunar Retroreflector), are designed to probe weak field – slow motion regime gravity in the Sun-Earth-Moon system through the measurement of Parametrized Post-Newtonian (PPN), Weak & Strong Equivalence Principles (WEP & SEP), Gdot/G, inverse-square law deviations, tests of GR and beyond, and implementation of lunar geodesy/geophysics. Tests have been performed in the last decades by the network of 3 Apollo and 2 Lunokhod laser retroreflector arrays. Imminent lunar surface missions and collaborations with ESA, ASI, NASA, will establish a solid heritage and basis for next-generation lunar reflectors, that will be evolved in the near future for GW detectors on the Moon like LGWA (Lunar Gravitational-wave Antenna), LSGA (Lunar Seismic and Gravitational Antenna) and iLILA (Laser Interferometer Lunar Antenna).
The acceleration of a jet to a relativistic velocity is a source of gravitational energy, jet-GWs, that has been largely left unexplored. Jet-GWs are memory-type signals with an amplitude of h~GE/c^4 d, where E is the energy of the accelerated jet, d is the distance to the source, G is Newton’s constant, and c is the speed of light and a characteristic time scale that depends on the acceleration time, the duration of the jet its opening angle and orientation. Among the most interesting sources of such gravitational waves are Gamma-Ray Bursts (GRBs) whose jets carry typically 10^51 erg. Jet-GWs can reveal how GRB jets are accelerated. Other interesting and less known sources are some Supernovae that harbor hidden jets, these jets don’t manage to penetrate the stars and are choked inside. As such they don’t have only indirect observational signatures. Jet-GW is the best way to directly reveal their existence. Jet-GW from both GRBs and Supernovae are in the deciHz to milliHz range making Lunar gravitational wave detectors best suited ideal for their detection.
Three types of seismic experiments, Passive Seismic Experiment (PSE), Active Seismic Experiment (ASE) and Lunar Surface Profiling Experiment (LSPE), were performed during the Apollo lunar landing missions from 1969 to 1972, and another experiment, Lunar Surface Gravimeter (LSG), designed to detect gravitational waves, also provided seismic data. Most of these instruments functioned till they were turned off in September of 1977, giving us continuous seismic data for up to eight years from five Apollo landing sites on the front (earth-facing) side of the moon. Four types of natural seismic events were observed: meteoroid impacts, thermal moonquakes, shallow moonquakes and deep moonquakes, and over 17,000 of those recorded on the PSE mid-period seismometers were catalogued. From these and 9 artificial-impact data, internal structure of the moon, seismic activities inside the moon and streams of meteoroids near the earth-moon system were estimated. The raw data, in the form of bit streams, were archived and are publicly available. Recently, these data were reformatted to standard seismic data format and made available to public. Re-analyses of these data using new analysis techniques and more powerful computers than what were available earlier are providing more detailed information on the interior structure of the moon. It is quite likely that further new information will be extracted from these half-century old data sets. New seismic observations on the moon are being planned to supplement what we now have.
Thursday, 20 April 2023
TBA
In this talk we will discuss the variety of astrophysical sources targeted by future deciHz gravitational wave detectors. We will focus in particular on different families of coalescing compact binaries, analysing their main properties, the features of the signals they are expected to emit in the deciHz band, and their phenomenology for fundamental astro-physics problems. For each class of sources we will also discuss potential multi-band scenarios, based on simultaneous observations with both space and ground based future detectors.
White dwarf-neutron star binaries represent a fascinating class of gravitational wave (GW) sources, showcasing diverse observational manifestations. They emerge from a complex, multi-stage process of massive stellar evolution. Before they spiral in due to GW emission, they may be observed as radio pulsars, gradually entering the GW bands. Upon contact, these systems may survive, giving rise to long-lived ultra-compact X-ray binaries that serve as valuable verification sources for gravitational waves within our Galaxy. Alternatively, if the white dwarf is too massive, the binary may merge, resulting in a gravitational wave burst and a faint supernova-like transient, most likely associated with the faint end of type Iax supernovae. Notably, the nuclear elements generated during these mergers, such as Mn55, play a role in shaping the chemical evolution of the Galaxy. In this presentation, I will provide a review of these intriguing systems, highlighting the latest advancements in population and interaction modelling and discussing their remarkable potential for gravitational wave detection.
Gravitational waves at decihertz frequencies are expected from many different astrophysical sources with a wide range of signal intensity and event statistics. These range from the solid predictions for low mass compact binaries to the uncertain statistics of IMBH or the more speculative GW signal from core collapse dynamics or jets related to SN explosion. In all cases, it is crucial that the search of GW signals is linked to a coordinated multi-wavelength strategy. The EM observations will contribute to establish the science cases, they will help to solve the degeneracy of the parameter estimate but also facilitate the GW detection by constraining the source location and/or temporal search window. I will give a (biased) overview of some of the science cases and of the opportunities offered by the new generation EM facilities.
The LIGO/Virgo-KAGRA collaboration operates ground based detectors which cover the frequency band from 10 Hz to the kHz regime. Meanwhile, the pulsar timing array and the soon to launch LISA mission will cover frequencies below 0.1 Hz, leaving a gap in detectable gravitational wave frequencies. Here we show how a laser interferometer on the moon (LION) gravitational wave detector would be sensitive to frequencies from sub Hz to kHz. We find that the sensitivity curve is such that LION can measure compact binaries with masses between 10 and 100M⊙ at cosmological distances, with redshifts as high as z = 100 and beyond, depending on the spin and the mass ratio of the binaries.
In this talk, I will present a review about gravitational wave emission from stars tidally disrupted by massive black holes (aka Tidal Disruption Events, TDEs), with a particular interest in the deciHertz regime. First, I will illustrate the main features of this signal and how the waveform is affected by the different parameters that describe these systems. Furthermore, I will show how these events can be a unique way to unveil the presence of intermediate mass black holes through the Universe and I will provide estimates of detection rates, considering both LGWA and other possible deci-Hertz interferometers. In addition to this, I will briefly mention gravitational lensing and how we expect to detect lensed TDEs in this frequency band, which could lead to a biased reconstruction of the astrophysical population. To conclude, I will talk about the TDE multimessenger emission and how we can use this information to constrain cosmological parameters (Toscani et al. 2023, in progress).
Lunar Gravitational-wave Antenna could become an important partner observatory for joint observations with future ground-based or space-borne laser interferometric detectors. Since it is going to be a new experiment, the writing of a scientific white paper is necessary in order to briefly outline mission and measurement concept, motivate sensitivity targets, and explain what will be the relation between LGWA and other GW detectors of the next decade and the synergies with other lunar missions. In this presentation we will present the planning and the expected contents of LGWA white paper.