Options
Erkal, Jessica
Preferred name
Erkal, Jessica
Official Name
Erkal, Jessica
Research Output
Now showing 1 - 5 of 5
- PublicationEIRSAT-1 - The Educational Irish Research Satellite(ESA, 2018-08-01)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The Educational Irish Research Satellite, "EIRSAT-1", is a collaborative space project that aims to build, launch and operate the first ever Irish satellite. The EIRSAT-1 spacecraft is a 2U CubeSat incorporating three novel experiment payloads: GMOD, a gamma-ray detector; EMOD, a thermal management coating demonstration; and WBC, an attitude control algorithm. The spacecraft is currently under construction at University College Dublin and will be delivered to ESA in late 2019.430 - PublicationInvestigating Jets and their Role in Star FormationIn this thesis, I present the results of a number of studies using high-resolution observations from world-class telescopes. The aim of these studies is to investigate protostellar jets and their role in star formation. In a case study of the bipolar jet from the T Tauri star DO Tau, we observe significant asymmetries in the morphology and kinematics of the jet and counterjet. The collimation of the jet supports the idea that magnetic fields collimate the jet, rather than pressure from the infalling envelope. If magnetic fields are responsible for jet collimation, then they may also drive jet launching. By measuring the radial velocities across the jet, we can calculate an upper limit on the jet launching radii. Our results support an X-wind or narrow disk wind model. Jet axis wiggling is also observed and is consistent with jet precession, which may be caused by an unseen companion in the disk or by launching the disk wind. In a study of four Class 0/I jets (HH 1, HH 34, HH 46 and HH 111) using high-resolution HST images, we were able to detect the inner knots of the red-shifted lobes in all four sources in more detail than previous studies. We compare these images to archival data to measure the proper motions in each jet. Jet axis wiggling is observed in three of these sources and the wiggling pattern in the HH 111 jet is consistent with jet precession and the presence of a companion in the disk. We also measure the extinction in each jet, which is quite high close to the star but decreases further out along each jet. Extinction measurements are important in the interpretation of emission line ratios, which reveal plasma conditions along the jet and hence the mass and momentum transfer. These two case studies illustrate the power of high resolution observations in differentiating between models of jet launching, and also reveal that protostellar jet trajectories could be a useful tool in identifying newly forming substellar companions close to the star. Finally, a survey of over 100 stars was conducted using high-resolution X-Shooter spectra. This study examines He I line profiles which vary between the two star forming regions examined in the sample, suggesting a trend with age. We also find that the maximum absorption velocity appears to be correlated with the source inclination and with the accretion rates of the sources. Our study confirms the results of past works (Edwards et al., 2006; Kwan et al., 2007; Fischer et al., 2008) and supports the idea that these winds are accretion powered. This survey gives context to our two case studies, by examining the link between accretion and ejection. High resolution observations are critical to advance understanding of the role of protostellar jets in star formation, as illustrated by the contribution of this thesis. The recently launched JWST facility marks the start of an era which will see exciting progress in this field, as its near-IR instruments peer deep into the embedded accretion-ejection engine.
38 - PublicationDevelopment and Validation of the Operations Procedures and Manual for a 2U CubeSat, EIRSAT-1, with Three Novel Payloads(2021-05-05)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The CubeSat standard, relatively short launch timescale, and orders of magnitude difference in cost in comparison to large scale missions, has allowed universities and smaller institutions to develop space missions. The Educational Irish Research Satellite (EIRSAT-1) is a 2U CubeSat being developed in University College Dublin (UCD) as part of the second round of the European Space Agency (ESA) Education Office’s Fly Your Satellite! (FYS) Programme. EIRSAT-1 is a student-led project to build, test, launch and operate Ireland’s first satellite. CubeSats typically use commercial off-the-shelf (COTS) components to facilitate new teams in developing a satellite on a rapid timescale. While some of the EIRSAT-1 subsystems are COTS procured from AAC Clyde Space, EIRSAT-1 has three novel experiments on-board which have been developed in UCD. The spacecraft’s Antenna Deployment Module has also been designed and built in-house. The on-board computer (OBC), procured from AAC Clyde Space, has been adapted to interface with these novel hardware components, accompanied by in-house developed software and firmware. All of these innovative subsystems complicate the CubeSat functionality making it essential to document and rigorously test the operations procedures for EIRSAT-1. In preparation for launch with these novel spacecraft subsystems, the EIRSAT-1 Operations Manual is being developed and incrementally verified. The Operations Manual contains the procedures to command and control the satellite, account for nominal and non-nominal scenarios and guide the operator in determining the cause of any anomalies observed during the mission and facilitate recovery. A series of operations development tests (ODTs) have been designed and conducted for a robust verification process. Each procedure is written up by a member of the EIRSAT-1 Operations Team in the EIRSAT-1 Operations Manual format. During an ODT, an in-flight scenario is considered in which the procedure under test is required. The procedure is then followed by a team member who has not been involved in the procedure development process. The feedback from these tests and from the operators is used to improve the procedures and continually update the Operations Manual. This paper will present the approach to operations development used by the EIRSAT-1 team and discuss the lessons learned for CubeSat operations development, testing and pre-flight verification.287 - PublicationDevelopment of the Ground Segment Communication System for the EIRSAT-1 CubeSat(2021-05-05)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The Educational Irish Research Satellite (EIRSAT-1) is a student-led project to design, build and test Ireland’s first satellite. As part of the development, a ground segment (GS) has also been designed alongside the spacecraft. The ground segment will support two-way communications with the spacecraft throughout the mission. Communication with the satellite will occur in the very high frequency (VHF) and the ultra high frequency (UHF) bands for the uplink and downlink respectively. Different modulation schemes have been implemented for both uplink and downlink as part of the GS system. Uplink incorporates an Audio Frequency Shift-Keying (AFSK) scheme, while downlink incorporates a Gaussian Minimum Shift-Keying (GMSK) scheme. In order for the spacecraft to successfully receive a telecommand (TC) transmitted from the ground station, a framing protocol is required. AX.25 was selected as the data link layer protocol. A hardware terminal node controller (TNC) executes both the AX.25 framing and the AFSK modulation. Keep It Simple Stupid (KISS) framing software was developed to allow data to be accepted by the TNC. A software defined radio (SDR) approach has been chosen for the downlink. GNURadio is software that allows flowcharts to be built to undertake the required signal processing of the received signal, the demodulation of the signal and the decoding of data. This paper provides a detailed account of the software developed for the ground segment communication system. A review of the AX.25 and KISS framing protocols is presented. The GNURadio flowcharts that handle the signal processing and data decoding are broken down and each constituent is explained. To ensure the reliability and robustness of the system, a suite of tests was undertaken, the results of which are also presented.292 - PublicationThe near-UV: The true window on jet rotation(Società Astronomica Italiana, 2017-01-01)
; ; ; High resolution observations of jet rotation in newly forming stars have the potential to support theories of magneto-centrifugal jet launching. We report a detection of a radial velocity difference across the blue-shifted jet from RY Tau, the direction of which matches the CO disk rotation sense. Now, in 3 of 3 cases, the sense of the near-UV jet gradient matches the disk rotation sense, implying that we are indeed observing jet rotation. It seems the jet core, probed at near-UV wavelengths, is protected by the outer jet layers from kinematic contaminations, and thus represents the only true window on jet rotation.78