We propose to search for temporal variations in HI absorption spectra seen against background pulsars to characterise Tiny Scale Atomic Structure (TSAS) in the Milky Way interstellar medium (ISM). We will re-observe seven previously studied bright pulsars at two observing epochs in this semester, resulting in minimum and maximum experimental baselines of 0.25 and 50 years. These observations will test predictions that there is a minimum size scale set by the thermal and turbulent properties of the ISM, below which TSAS is only sporadically seen, and will potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. By using a new phase-resolved spectral line mode that we have recently implemented on Parkes, we will cut data rates and processing times by factors of ~1000. Following the success of this pilot project, we plan to expand to a long-term monitoring programme. Successful demonstration of our techniques will lay the groundwork for future programmes on the SKA.

We propose to search for temporal variations in HI absorption spectra seen against background pulsars to characterise Tiny Scale Atomic Structure (TSAS) in the Milky Way interstellar medium (ISM). We will re-observe seven previously studied bright pulsars at two observing epochs in this semester, resulting in minimum and maximum experimental baselines of 0.25 and 50 years. These observations will test predictions that there is a minimum size scale set by the thermal and turbulent properties of the ISM, below which TSAS is only sporadically seen, and will potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. By using a new phase-resolved spectral line mode that we have recently implemented on Parkes, we will cut data rates and processing times by factors of ~1000. This project successfully observed in 2024APR and will be expanded to a Long Term Project when that scheme reopens for applications in 2025APR. Successful demonstration of our techniques will lay the groundwork for future programmes on the SKA.

We propose to search for temporal variations in HI absorption spectra seen against background pulsars to characterise Tiny Scale Atomic Structure (TSAS) in the Milky Way interstellar medium (ISM). We will re-observe seven previously studied bright pulsars at two observing epochs in this semester, resulting in minimum and maximum experimental baselines of 0.25 and 50 years. These observations will test predictions that there is a minimum size scale set by the thermal and turbulent properties of the ISM, below which TSAS is only sporadically seen, and will potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. By using a new phase-resolved spectral line mode that we have recently implemented on Parkes, we will cut data rates and processing times by factors of ~1000. This project successfully observed in 2024APR and will be expanded to a Long Term Project when that scheme reopens for applications in 2025APR. Successful demonstration of our techniques will lay the groundwork for future programmes on the SKA.

The atomic interstellar medium shows tiny-scale optical depth fluctuations on the scale of 0.1~10,000 AU, whose origin and nature are poorly understood. The existence of this Tiny-Scale Atomic Structure (TSAS) has significant implications, potentially calling into question our fundamental understanding of heating, cooling and dynamical processes in the interstellar medium. Yet observations remain sparse. This long-term project plans to search for temporal variations in HI absorption spectra seen against background pulsars to characterise TSAS in the Milky Way interstellar medium (ISM). These observations constitute the largest number of sightlines and densest temporal sampling ever performed in a single experiment, and will test predictions that TSAS is the tail end of a turbulent cascade, constrain its minimum size scale (down to resolutions of ~0.05 AU) and potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. We make use of the phase-resolved spectral line mode that we have recently implemented on Parkes, which has cut data rates and processing times by factors of ~1000 compared to past studies. This is an expansion of our pilot P1321 to a long term study.

We request time to observe 270 pulsars on a regular basis in order to achieve three main science goals. The first is to understand pulsars: how do they spin down and what disrupts this process, how and why their profiles vary with time, whether they precess or have planetary mass companions, in short all the things that make pulsar timing noisier than the perfect clock. Secondly we want to understand the interstellar medium of our Galaxy through repeated monitoring of dispersion measure, rotation measure and flux density variations in conjunction with scintillation parameters. Finally, we provide these data as a community service both to the high-energy community where we have strong collaborative links (particularly to Fermi) and to the radio pulsar astronomers generally through the CSIRO archive. The project is on-going since 2007, we are (co-)authors on 106 papers arising from the P574 data. The data have contributed to the PhD theses of students from Bordeaux, Manchester, Oxford, Stanford, and Swinburne. We are seeking long-term project status with a view to continuing the project into the SKA era.

With supreme timing stabilities, millisecond pulsars (MSPs) have been used to test gravitational theories, and to collectively probe the stochastic gravitational-wave background (GWB) at the nano-Hz regime. Recent years have seen the major pulsar timing array (PTA) consortia closing in on high-significance detections of the GWB, which marks the dawn of a new GWB era. To deepen our understanding of the sources of the GWB requires steady enhancement of the PTA sensitivity. The best strategy to sustain the enhancement is to continuously add new qualified MSPs to the PTAs. VLBI (very long baseline interferometry) astrometry of MPSs would empower this strategy by refining the pulsar timing model with precise astrometric measurements obtained in a relatively short timeline. In addition, VLBI astrometry of MSPs contributes to MSP-related/based studies in many ways: it can strengthen the tests of gravitational theories, probe the formation channels of millisecond pulsars, refine the Galactic interstellar medium distribution, and even sharpen the constraints on the Galactic dark matter distribution. So far, 24 MSPs have been astrometrically determined with VLBI. As the only southern-hemisphere-based VLBI network, the LBA has only contributed to one astrometric determination of MSPs. We propose to carry out the first LBA astrometric survey of MSPs, which will benefit the aforementioned scientific aspects, and significantly reduce sky-position-related selection effects on statistical studies based on MSP astrometry. This proposal aims at piloting the astrometric survey by observing 28 MSP candidates at 13cm.

This proposal aims to measure the parallax of pulsar B1055-52. PSR B1055-52 is particularly important for studying neutron star properties. Bright at radio and gamma-rays, the pulsar is also well detected at near-infrared, optical, UV and X-ray frequencies. In X-rays, we even can see the surface's thermal emission and can investigate the non-uniformity of the temperature distribution over rotation phase. Since PSR B1055-52 is a rare interpulse pulsar, there is an exceptionally good constraint on the angle between the magnetic dipole and rotation axes, allowing to resolve many model degeneracies. The wealth of observational data enable a very detailed investigation of this pulsar and neutron stars in general. However, these investigations cannot be completed without one essential parameter - the distance. Currently, the possible distance range obtained from the dispersion measure has a span of almost a factor 10 if different Galactic electron density models are considered. At the same time, there are several indicators that PSR B1055-52 is close enough to obtain a parallax-based distance with high accuracy.

With this proposal we ask time to continue our timing follow-up campaign of pulsars discovered with the MeerKAT telescope. Fourtytwo sources have been discovered in targeted observations of Fermi unidentified point sources, two towards Supernova Remnants, 19 in the Magellanic Clouds, 105 in Globular Clusters and 81 in a survey of the Galactic plane. A large fraction of the new discoveries are recycled pulsars (including a few relativistic systems and several 'spider' binaries), or young pulsars. Timing observations have an essential role in exploiting the full potential of any pulsar discovery, allowing for the precise measurement of rotational, astrometric and orbital parameters which, in turn, give us powerful tools to improve our understanding of the physics in extreme environments as well as of the population of neutron stars as a whole. The UWL receiver of the Parkes telescope is a sensitive, versatile instrument that is allowing us to successfully time these new sources, in the bright-end of TRAPUM discoveries.

With this proposal we ask time to continue our timing follow-up campaign of pulsars discovered with the MeerKAT telescope. Fourtytwo sources have been discovered in targeted observations of Fermi unidentified point sources, two towards Supernova Remnants, 19 in the Magellanic Clouds, 105 in Globular Clusters and 81 in a survey of the Galactic plane. A large fraction of the new discoveries are recycled pulsars (including a few relativistic systems and several 'spider' binaries), or young pulsars. Timing observations have an essential role in exploiting the full potential of any pulsar discovery, allowing for the precise measurement of rotational, astrometric and orbital parameters which, in turn, give us powerful tools to improve our understanding of the physics in extreme environments as well as of the population of neutron stars as a whole. The UWL receiver of the Parkes telescope is a sensitive, versatile instrument that is allowing us to successfully time these new sources, in the bright-end of TRAPUM discoveries.

The propagation effects of the ionized interstellar medium (IISM) on pulsars are not well understood, and increase uncertainty on pulsar timing measurements. As high-precision pulsar timing is critical for using pulsars to detect phenomena as varied as gravitational waves and neutron star glitches, it is important to improve our understanding of these propagation effects. One such effect is chromatic dispersion, which contributes to timing noise but has been detected only once. We propose a set of 4 pointings with the Murriyang 64m Parkes Radio Telescope Ultra-Wide bandwidth Low frequency receiver (UWL), totaling 10 hours of telescope time. Our three targets are all strongly polarized pulsars in the Galactic plane, selected to maximize our chances of detecting one or both of the two types of chromatic dispersion. Non-detections will place upper limits on magnetic field strength and electron density in the IISM.