ICTS

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.

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.

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
 

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.

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.

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.

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.

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).