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Earth's dynamic oblateness (J2) had been undergoing a decrease, according to space geodetic observations over the past 25 years, until around 1998, when it switched quite suddenly to an increasing trend that has continued to the present. The secular decrease in J2 resulted primarily from the postglacial rebound in the mantle. The present increase, whose geophysical cause(s) are uncertain, thus signifies a large change in global mass distribution with a J2 effect that considerably overshadows that of mantle rebound.

[1] The GRACE mission is designed to monitor mass flux on the Earth's surface at one month and high spatial resolution through the estimation of monthly gravity fields. Although this approach has been largely successful, information at submonthly time scales can be lost or even aliased through the estimation of static monthly parameters. Through an analysis of the GRACE data residuals, we show that the fundamental temporal and spatial resolution of the GRACE data is 10 days and 400 km. We present an approach similar in concept to altimetric methods that recovers submonthly mass flux at a high spatial resolution. Using 4°Â 4°blocks at 10-day intervals, we estimate the mass of surplus or deficit water over a 52°Â 60°grid centered on the Amazon basin for July 2003. We demonstrate that the recovered signals are coherent and correlate well with the expected hydrological signal. Citation: Rowlands, D. D., S. B.

Cox and Chao [2002] reported the detection of a large anomaly in the time series of Earth's dynamic oblateness J2, the lowest‐degree gravity spatial harmonic, in the form of a positive jump since 1998 overshadowing the decreasing secular trend in J2 caused primarily by the postglacial rebound (PGR). Here we report that recent data show that J2 has been rapidly returning toward “normal” (with PGR considered) since early 2001. In search of the geophysical and climatic causes for this “1998–2002 J2 anomaly,” we report an oceanographic event that took place in the extratropic north and south Pacific basins that was found to match remarkably well with the time evolution of the anomaly. We examine the leading (nonseasonal, extratropic Pacific) Empirical Orthogonal Function/Principal Component modes in the sea‐surface height (SSH) data from TOPEX/Poseidon, sea surface temperature (SST) data from the National Center for Environmental Predictions, and output fields of the Estimating the Circulation and the Climate of the Ocean (ECCO) ocean general circulation model (OGCM), including ocean bottom pressure (OBP) and temperature and salinity profiles. The phenomenon appears to be part of the Pacific Decadal Oscillation, and temporal correlations are made. However, quantitatively, the OBP field of the ECCO model predicts a J2 anomaly that is smaller in magnitude than the observed by a factor of about 3. We discuss various possibilities for reconciling this discrepancy in terms of inadequacies of present OGCMs and considering other geophysical contributions; a complete resolution of the J2 enigma awaits further studies.

This is the second of two companion papers that describe the development of the RemoveDEBRIS space mission. This second article describes the in-orbit operations that were performed to demonstrate technologies to be used for the active removal of space debris, whereas the first paper described the development of the satellite's hardware. The RemoveDebris mission has been the world's first Active Debris Removal (ADR) mission to successfully demonstrate, in orbit, some cost effective technologies, including net and harpoon capture; and elements of the whole sequence of operations, like the visionbased navigation. The satellite was launched the 2 nd of April 2018, to the International Space Station (ISS) and from there, on the 20 th of June 2018, was deployed via the NanoRacks Kaber system into an orbit of 405 km altitude. During the mission, two 2U CubeSats have been released by the mothercraft platform as artificial debris targets, to demonstrate net capture and cameras to be used for vision based navigation. Harpoon capture has been demonstrated by deploying a target and then firing at it a harpoon tethered to the platform. The various phases of the missions have been monitored using relevant telemetry and video cameras, and this paper reports the results of the various demonstrations.

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This essay updates Raymond Williams’ flow by defining its contemporary logics – televisible and invisual. The televisible are both media content and visual digital media forms that shape – and are shaped by – interactions with media content through digital media platforms. The invisual are unseen operations of software, algorithms and other processes that configure and manifest the televisible. A case study of Netflix illuminates how this reconceived flow series functions as a framework for understanding the stakes of digital media platforms that both foster possibilities for user interactivity and attenuate users to industrial models for audienceship and programming.

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