The GeoClaw software for depth-averaged flows with adaptive refinement

Many geophysical flow or wave propagation problems can be modeled with two-dimensional depth-averaged equations, of which the shallow water equations are the simplest example. We describe the GeoClaw software that has been designed to solve problems of this nature, consisting of open source Fortran programs together with Python tools for the user interface and flow visualization. This software uses high-resolution shock-capturing finite volume methods on logically rectangular grids, including latitude--longitude grids on the sphere. Dry states are handled automatically to model inundation. The code incorporates adaptive mesh refinement to allow the efficient solution of large-scale geophysical problems. Examples are given illustrating its use for modeling tsunamis, dam break problems, and storm surge. Documentation and download information is available at www.clawpack.org/geoclawComment: 18 pages, 11 figures, Animations and source code for some examples at http://www.clawpack.org/links/awr10 Significantly modified from original posting to incorporate suggestions of referee

Unlocking the Next Generation of Nano-Satellite Missions with 320 Mbps Ka-Band Downlink: On-Orbit Results

Relatively low downlink data rates have historically limited the scientific and commercial return from CubeSats and SmallSats. As the capability of payloads for these satellites continues to increase, high-speed downlink capability is required to realize the increasing potential from these systems. In this paper we present the on-orbit results of our high-speed Ka-band transmitter operating aboard the twin Corvus-BC3 and Corvus-BC4 6U CubeSats. The 1-U form factor Ka-band system enables the unprecedented data return from a multi-spectral imager in this class of spacecraft. We highlight the spacecraft design and operational challenges that have been overcome on these missions that will enable high-speed downlink on any CubeSat or SmallSat. While the pointing requirements for this Ka-band downlink are readily achievable by today’s small satellites, we discuss some of the hidden complexities on both the attitude determination and control system (ADCS) as well as on the ground segment. Currently in-place ground infrastructure, including a 2.8 m dish at a downlink station in Svalbard, Norway, has enabled rapid commissioning and on-demand downlink several times a day for these sun-synchronous spacecraft. This paper includes flight data from early commission to routine operation at high-data rates. We believe the lessons learned on these missions will be valuable for other CubeSat developers that plan on moving away from UHF, S-band, and X-band and into the realm of millimeter microwave frequencies (such as 27 GHz)

Ka-Band for CubeSats

As 3U and 6U CubeSat missions begin to play a fundamental role in space science, advanced applications and even commercial utilization, there is a strong corresponding demand for higher data rates from even smaller fractions of the volume of a Cubesat envelope. Based on a concept outlined at this conference in 2012, a Ka-Band transmitter for Earth Exploration applications has now been developed and tested and this RF technology is now in-orbit; flying as a major demonstration in a 6U spacecraft. Since this technology is capable of providing tens of GBytes per day of downlinked data from a single 3U, 6U or 12U cubesat system, the future is even brighter. We will review in this presentation what has been accomplished to date, the challenges associated with using Ka-Band and where this technology is headed in the immediate future. This paper also demonstrates the effectiveness of Ka-Band for satellite interlinks (space-to-space relay) and the ultimate advantage of mmW to deep space communications using very small systems. A less obvious advantage of Ka-Band: spectrum management via spot beam frequency reuse is also of prime importance to the community. This aspect of mmW technology will also be examined and a plan for future spectrum utilization will be outlined

An Evaluation of CubeSat Orbital Decay

Accurate orbit lifetime assessment is necessary to support satellite mission design, concepts-of-operation, and post-mission debris mitigation strategies. Because of their standardized form factors, the 47 CubeSats placed in orbit since 2003 provide a unique opportunity to study the accuracy of such orbit lifetime techniques in a controlled manner. In this study we examine CubeSat assessments for both IADC and ISO standards compliance and actual orbital decay estimation compared to empirical Space Surveillance Network observations

Clawpack Source Code

Repository for released versions of the Clawpack software. For documentation, see http://www.clawpack.org. For current development, see https://github.com/clawpack. This project provides a single DOI for all recent releases of Clawpack. The tar files archived here are also archived in Zenodo with a distinct DOI for each release. See http://www.clawpack.org/releases.html for DOIs, links, and release notes

Global Educational Network for Satellite Operations (GENSO)

The GENSO project is an international project that officially began in October 2006. The main goal of the project is to improve educational spacecraft communications by creating an international network of university and amateur ground stations. With the realization of such a network, more experimental data can be downloaded, a greater number of students can participate in realtime spacecraft mission operations with a hands-on approach, and new scientific missions can be realized

Deployment of CubeSat Constellations Utilizing Current Launch Opportunities

Large sensor constellations are being proposed as a natural application of CubeSat class spacecraft. Given their low cost and numerous launch opportunities large numbers of CubeSats can be easily deployed in orbit. However, the fact that CubeSats are launched as secondary payloads limits the options for their deployment in appropriate constellation geometries. This problem is further aggravated given the current lack of propulsive options for CubeSats. This paper explores the viability of deploying constellations of cubeSats with efficient geometries using current secondary launch opportunities. The only variables being considered are the deployment timing and direction for individual CubeSats in a single launch. The results indicate that simple deployment strategies can be utilized to provide appropriate CubeSat dispersion to create efficient constellation geometries

Enabling Flexible Secondary Launches with the CubeSat Standard

CubeSats are currently forced to follow the traditional secondary payload model. In this model secondary payloads must identify a particular launch opportunity with a primary. The secondary payloads must commit to the launch and are subjected to any delays solely due to the primary. Additionally, this secondary payload paradigm is forcing suboptimal use of excess launch capacity since it complicates the process to add additional secondary payloads close to the launch date. This situation does not scale to support the growing demand for CubeSat launches that could potentially reach 100s of CubeSats per year within the next few years. A more flexible secondary launch model is required to support the CubeSat community and provide the fast access to space made possible by the CubeSat standard. This flexible model will allow developers to focus on the development of their spacecraft. Several key developments are necessary to reach a truly flexible secondary launch capability including technical, political, and regulatory issues. Some of the most critical are currently being addressed by work being performed by Cal Poly and their industrial and government partners

Recent CubeSat Launch Experiences on U.S. Launch Vehicles

CubeSats are currently required to follow the traditional secondary payload model. In this model, secondary payloads must identify a particular launch opportunity with a primary. The secondary payloads must commit to the launch and are subjected to any delays solely due to the primary. Additionally, this secondary payload paradigm is forcing suboptimal use of excess launch capacity since it complicates the process to add additional secondary payloads close to the launch date. This situation does not scale to support the growing demand for CubeSat launches that could potentially reach 100s of CubeSats per year within the next few years. A more flexible secondary launch model is required to support the CubeSat community and provide the fast access to space made possible by the CubeSat standard. This flexible model will allow developers to focus on the development of their spacecraft. Several key developments are necessary to reach a truly flexible secondary launch capability including technical, political, and regulatory issues. Some of the most critical are currently being addressed by work being performed by Cal Poly and their industrial and government partners