Development of University-Friendly CubeSat Bus and Ground Station Architecture Using Software-Defined Radios

The goal of the research and development presented in this paper is to introduce a CubeSat bus and ground station architecture that is made to be much more approachable to schools and universities. The three main pillars of the effort are low-cost, maintaining flexibility, and lowering the bar of entry. The presented CubeSat bus includes PyCubed board which houses most of the core satellite bus components on a single board. The board can handle main processing, data storage, UHF radio communication, telemetry sensors, and power management. This UHF radio is paired with a software-defined radio (SDR) that serves as the ground station radio. For a faster data rate downlink of payload data, a low-cost SDR (Ettus B205mini) is paired with a RaspberryPi processor. By leveraging the flexibility of SDRs, one SDR at the ground station is agile enough to provide UHF up/downlink for the CubeSat bus comm, as well as receiving S- or X-band payload data downlink. This proposed architecture will enable project teams to rapidly achieve a baseline capability with the satellite bus such that the development schedule and cost can be drastically reduced while providing the students with the full-cycle experience of satellite engineering

An Exploration of the Small Satellite Value Chain and the Future of Space Access

“Space is hard” is a saying that has been made popular in the last few years. It is not just the engineering that is challenging, but also applies to the business of space as well. From supply chain to regulation, the space industry’s infrastructure is not prepared to handle the influx of demand forecasted through the next decade, especially in the small satellite segment. Accordingly, space businesses are looking to cost effectively and quickly build and deploy space payloads while being able to refresh their technologies as advancements are made on Earth. In this paper, we will explore a small satellite customer’s journey from ideation to launch and operations including a survey of the commercial and government entities involved. We will discuss the costs associated with the current processes from both a financial and schedule perspective. An important aspect to this study is to understand that there are many trade-offs to be made, from a whole turn-key solution from ideation to operations, to an entire a la carte solution with space customers “DIY-ing” it. We will provide a broad overview of the providers in each of the value chain segments from payload development, manufacturers, testing, regulatory, launch, and operations. Finally, we will discuss opportunities to make space access easier and the outlook of the value chain as space commercialization becomes a reality over the next decade, including new impactful technologies such as on-orbit servicing and repair. Reusable infrastructure is the key to solving these customers’ pain points as satellites are disposable assets today

On Sub-ENSO Variability

Multichannel singular spectrum analysis (MSSA) of surface zonal wind, sea surface temperature (SST), 20° isotherm depth, and surface zonal current observations (between 1990 and 2004) identifies three coupled ocean–atmosphere modes of variability in the tropical Pacific: the El Niño–Southern Oscillation (ENSO), the annual cycle, and a mode with a 14–18-month period, which is referred to as sub-ENSO in this study. The sub-ENSO mode accounts for the near 18-month (near annual) variability prior to (following) the 1997/98 El Niño event. It was strongest during this El Niño event, with SST anomalies exceeding 1°C. Sub-ENSO peak SST anomalies are ENSO-like in structure and are associated with eastward propagating heat content variations. However, the SST anomalies are preceded by and in near quadrature with relatively strong remotely forced westward propagating zonal current variations, suggesting the sub-ENSO mode arises from the zonal-advective feedback. The sub-ENSO mode is found to exist also in an intermediate complexity model (ICM) of the tropical Pacific. A heat budget analysis of the model’s sub-ENSO mode shows it indeed arises from the zonal-advective feedback. In the model, both ENSO and sub-ENSO modes coexist, but there is a weak nonlinear interaction between them. Experiments also show that the observed changes in sub-ENSO’s characteristics may be explained by changes in the relative importance of zonal and vertical advection SST tendencies

Mixing of Ground States in Vertex Models

We consider the analogue of the 6-vertex model constructed from alternating spin n/2 and spin m/2 lines, where $1\leq n<m$. We identify the transfer matrix and the space on which it acts in terms of the representation theory of $U_q(sl_2)$. We diagonalise the transfer matrix and compute the S-matrix. We give a trace formula for local correlation functions. When n=1, the 1-point function of a spin m/2 local variable for the alternating lattice with a particular ground state is given as a linear combination of the 1-point functions of the pure spin m/2 model with different ground states. The mixing ratios are calculated exactly and are expressed in terms of irreducible characters of $U_q(sl_2)$ and the deformed Virasoro algebra.Comment: 12 pages, LaTeX, typos correcte