skip to main content

Search for: All records

Award ID contains: 1936665

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. With space more accessible than ever, academic institutions like the University of Colorado (CU) Boulder have exhibited that CubeSats (compact, homogeneous, rectangular satellites with masses below 14 [kg]) can be leveraged for remarkable space missions capable of making significant advances to both scientific and technological fields. One such CubeSat project is the NSF-funded Space Weather Atmospheric Reconfigurable Multiscale Experiment (SWARM-EX), which will launch three 3U CubeSats into a “swarm” that will demonstrate autonomous formation flying capabilities while simultaneously studying the spatial and temporal variability of ion-neutral interactions in the equatorial Ionosphere-Thermosphere region. Although the small stature of CubeSats and their standardized deployer options help to lower unit development cost and facilitate launch opportunities, the physical size limits of CubeSats prove to be a double-edged sword vis-à-vis sustaining a stable power state while hosting instruments with high power demands and often strict pointing requirements. For SWARM-EX, this issue is magnified by the mission’s ambitious goals; to comply with mission requirements, a SWARM-EX spacecraft is required to concurrently (1) point the science instruments no more than 30° off ram when they are operational, (2) point the GNSS patch antenna no more than 30° off zenith when the spacecraft are separated by ≤more »10 [km], (3) point the X-Band patch antenna no more than 18° off boresight from the ground station during downlink, (4) maximize the differential ballistic coefficient during differential drag maneuvers, and (5) maximize solar array power generation at all times. Consequently, advanced CubeSat Missions like SWARM-EX require innovative systems engineering solutions to remain power-positive during on-orbit operations. Through a combination of intricate pointing profiles, orbital simulations, a comprehensive and coordinated ConOps, battery state of charge simulation tools, and expertise from previous CubeSat missions, the SWARM-EX team has conceived a plan to successfully meet all these mission requirements; it is the aim of the authors to illuminate these strategies as a case study.« less
    Free, publicly-accessible full text available September 5, 2023
  2. Radiation poses known and serious risks to smallsat survivability and mission duration, with effects falling into two categories: long-term total ionizing dose (TID) and instantaneous single event effects (SEE). Although literature exists on the topic of addressing TID in smallsats, few resources exist for addressing SEEs. Many varieties of SEEs exist, such as bit upsets and latch ups, which can occur in any electronic component containing active semiconductors (such as transistors). SEE consequences range from benign to destructive, so mission reliability can be enhanced by implementing fault protection strategies based on predicted SEE rates. Unfortunately, SEE rates are most reliably estimated through experimental testing that is often too costly for smallsat-scale missions. Prior test data published by larger programs exist, but may be sparse or incompatible with the environment of a particular mission. Despite these limitations, a process may be followed to gain insights and make informed design decisions for smallsats in the absence of hardware testing capabilities or similar test data. This process is: (1) Define the radiation environment; (2) identify the most critical and/or susceptible components on a spacecraft; (3) perform a search for compatible prior test data and/or component class data; (4) evaluate mission-specific SEE rates frommore »available data; (5) study the rates alongside the mission requirements to identify high-risk areas of potential mitigation. The methodology developed in this work is based on the multi-institutional, National Science Foundation (NSF) Space Weather Atmospheric Reconfigurable Multiscale Experiment (SWARM-EX) mission. The steps taken during SWARM-EX’s radiation analysis alongside the detailed methodology serve as a case study for how these techniques can be applied to increasing the reliability of a university-scale smallsat mission.« less
    Free, publicly-accessible full text available August 1, 2023
  3. This paper presents a wideband circularly polarized antenna for small satellites to be used with NASA Near- Earth Networks (NEN). This single-fed stacked antenna utilizes the electromagnetic coupling concept and is usable with a duplex transceiver. The circularly-polarized antenna employs hybrid perturbations on stacked patches and covers NASA NEN’s both uplink and downlink frequencies, thus replacing the conventional requirement of two separate antennas. It provides a notable wide axial ratio (AR) < 3 dB bandwidth of 1.16 GHz from 7.02 GHz to 8.18 GHz (15.3%). The optimized patch dimensions provide 34.6% VSWR ~ 2 bandwidth from 6,525 MHz to 9,253 MHz. The overall antenna size is 17 mm × 17 mm × 6.6 mm, and has a peak gain of 7.9 dBi. This proposed antenna will overcome solar cell space constraint on smallsat’s outer wall by saving at least 50% area required by the conventional two-antenna method.
    Free, publicly-accessible full text available February 16, 2023
  4. A hybrid perturbation scheme is used in this article to achieve wide axial ratio (AR) bandwidth and beamwidth from circularly polarized (CP) microstrip patch–ring antennas using a single probe feed. Perturbations in the diagonal corners of a square ring and a square patch arranged in a stacked configuration are introduced to achieve the circular polarization. First, an enhanced AR bandwidth is obtained when a combination of a square ring and a square patch with negative perturbations is used as parasitic and driven elements, respectively. Next, circular polarization with wider AR bandwidth, wider beamwidth, and lower cross-polarization is obtained when a combination of a driven square patch with positive perturbation and a parasitic square ring with negative perturbations, termed as hybrid perturbations, is used. This antenna has a footprint suitable for small satellite applications (e.g., CubeSats) and its operating frequencies cover the allocated S-band downlink frequencies of NASA Deep Space Network and NASA Near Earth Network.
  5. The Space Weather Atmospheric Reconfigurable Multiscale Experiment (SWARM-EX) is a National Science Foundation (NSF) sponsored CubeSat mission distributed across six colleges and universities in the United States. The project has three primary goals: (1) contributing to aeronomy and space weather knowledge, (2) demonstrating novel engineering technology, and (3) advancing higher education. The scientific focus of SWARM-EX is to study the spatial and temporal variability of ion-neutral interactions in the equatorial Ionosphere-Thermosphere (I-T) region. Since the mission consists of three spacecraft operating in a swarm, SWARM-EX will take in-situ measurements of the neutral and ion composition on timescales of less than an orbital period to study the persistence and correlation between different phenomena in the I-T region. The engineering objectives of SWARM-EX are focused on advancing the state of the art in spacecraft formation flying. In addition to being the first passively safe, autonomous formation of more than two spacecraft, SWARM-EX will demonstrate several other key innovations. These include a novel hybrid propulsive/differential drag control scheme and the realization of a distributed aeronomy sensor. As a project selected by the NSF for its broader impacts as well as its intellectual merit, SWARM-EX aims to use CubeSat development as a vehicle formore »education. The six collaborating institutions have varying levels of CubeSat experience and involve students who range from first-year undergraduates to Ph.D. candidates. These differences in knowledge, as well as the distributed nature of the program, present a tremendous educational opportunity, but also raise challenges such as cross-institutional communication and coordination, document sharing and file management, and hardware development. By detailing its procedures for overcoming these challenges, the SWARM-EX team believes that it may serve as a case study for the coordination of a successful CubeSat program distributed across multiple institutions.« less