Now showing 1 - 7 of 7
  • Publication
    Development of the Ground Segment Communication System for the EIRSAT-1 CubeSat
    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.
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  • Publication
    Development of a Nanosatellite System Modeling Architecture for EIRSAT-1
    Over the last two decades, CubeSats which are nanosatellites with form factors based on units (U) of 10 x 10 x 10 cm3, have become more common in academia, enabling students to gain hands-on experience with satellite design, testing and deployment [15]. The use of Commercial-Off-TheShelf (COTS) components reduces development cost and time, making CubeSats an accessible and cost effective route to space. CubeSats are increasingly important for in-orbit demonstrations of new technologies. Further, their flexibility allows them to be configured for a wide range of science mission profiles, either as a standalone platform, as a communications relay for lunar and inter-planetary missions, such as NASA's Mars Cube One (MarCO) satellites [14], or as a daughter spacecraft to study a near-Earth object such as LICIACube [2]. Several CubeSats for high energy astrophysics are currently in orbit and in development [9].
      18
  • Publication
    Update on the status of the Educational Irish Research Satellite (EIRSAT-1)
    The Educational Irish Research Satellite, EIRSAT-1, is a 2U CubeSat being implemented by a student-led team at University College Dublin, as part of the 2nd round of the European Space Agency’s Fly Your Satellite! programme. In development since 2017, the mission has several scientific, technological and outreach goals. It will fly an in-house developed antenna deployment module, along with three custom payloads, which are integrated with commercial off-the-shelf subsystems. In preparation for the flight model, a full-system engineering qualification model of the spacecraft has undergone an extensive period of test campaigns, including full functional tests, a mission test, and environmental testing at the European Space Agency’s CubeSat Support Facility in Redu, Belgium. Beyond the technical, educational, and capacity-building goals of the mission, EIRSAT-1 aims to inspire wider study of STEM subjects, while highlighting the importance of multidisciplinary teams and creating greater awareness of space in everyday life. A wide range of outreach activities are being undertaken to realise these aims. This paper provides a status update on key aspects of the EIRSAT-1 project and the next steps towards launch.
      29
  • Publication
    Development and Validation of the Operations Procedures and Manual for a 2U CubeSat, EIRSAT-1, with Three Novel Payloads
    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.
      484
  • Publication
    A new approach to modal analysis of uniform chain systems
    (Elsevier, 2008-04-08) ;
    A new method is presented to determine the mode shapes and frequencies of uniform systems consisting of chains of masses and springs of arbitrary number with arbitrary boundary conditions. Instead of the classical eigenproblem approach, the system is analysed in terms of circulating waves and associated phase lags. The phasor conditions for the establishment of standing waves determine the vibration modes. The conditions fully specify their shapes and frequencies, and lead to simple, explicit expressions for the components of the modal vectors and the associated natural frequencies. In addition, the form of the phasor diagrams of the modes gives insight into the modal behaviour. The orthogonality of mode shapes also readily emerges. Examples are presented for different boundary conditions. Although not presented, it is possible to extend the approach to non-uniform lumped systems and to forced frequency responses.
    Scopus© Citations 8  1179
  • Publication
    Wave-based control of non-linear flexible mechanical systems
    The need to achieve rapid and accurate position control of a system end-point by an actuator working through a flexible system arises frequently, in cases from space structures to disk drive heads, from medical mechanisms to long-arm manipulators, from cranes to special robots. The system’s actuator must then attempt to reconcile two, potentially conflicting, demands: position control and active vibration damping. Somehow each must be achieved while respecting the other’s requirements. Wave-based control is a powerful solution with many advantages over previous techniques. The central idea is to consider the actuator motion as launching mechanical waves into the flexible system while simultaneously absorbing returning waves. This simple, intuitive idea leads to robust, generic, highly efficient, adaptable controllers, allowing rapid and almost vibrationless re-positioning of the remote load (tip mass). This gives a generic, high-performance solution to this important problem that does not depend on an accurate system model or near-ideal actuator behaviour. At first sight wave-based control assumes superposition and therefore linearity. This paper shows that wave-based control is also robust (or can easily be made robust) to non-linear behaviour associated with non-linear elasticity and with large-deflection effects.
      1461Scopus© Citations 30
  • Publication
    EIRSAT-1 - The Educational Irish Research Satellite
    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.
      514