GEOS-C C-band transponder prelaunch calibration and test data

The delay characteristics and spacecraft telemetry housekeeping data for the GEOS-C C-Band transponders are presented. The data are presented in graphical form to provide a convenient method for computing radar range measurement corrections as a function of signal strength at the transponder and spacecraft environment. The data are also presented in tabular form along with the mathematical models used to derive the curves. Also included are a list of the operating characteristics of each transponder and a description of the calibration test equipment set-up

GEOS-C coherent C-band transponder test procedure for spacecraft level tests

Procedures for the performance of two tests (electrical and airlink) for the transponder are outlined. The C-band test console used in performing the above tests is described (circuit diagrams and block diagrams), and equipment specifications are given. Calibration of the test equipment is also discussed

GEOS-C noncoherent C-band transponder test procedure for spacecraft level tests

Test procedures necessary for the calibration and performance verification of the noncoherent C-band transponders after spacecraft hardware integration, but prior to spacecraft/launch vehicle integration are presented

Advanced altimetry

The radar altimeter being developed for the Ocean Topography Experiment (TOPEX) will have an inherent instrument precision of 2 to 3 cm. While some minor refinements may be possible in the future, major geophysical advances could be made if altimetric measurements over a wide swath of the Earth's surface were possible. The NASA Headquarters Oceanic Processes Branch is supporting a 3-year investigation of the technological issues inherent in the precision measurement of topography from spaceborne platforms at angles off-nadir. To explore the off-nadir measurement of topography, a flexible, airborne radar instrument system is being developed. Its hardware design is now complete, and it is made up of several subsystems. The antenna selected is a dielectric lens of .894 m diameter. The RF subsystem uses phase-locked oscillators, FET solid-state amplifiers, and times four frequency multipliers to develop a transmit signal at a frequency of 36.0 GHz and a local oscillator signal at a frequency of 35.4 GHz. Lecroy 6880 digitizers under computer control digitize the five receiver outputs. The digital subsystem consists of six single-board Heurikon processors. At this time, the instrument construction continues with final system integration planned for November 1988

Grassroots Agency: Participation and Conflict in Buenos Aires Shantytowns seen through the Pilot Plan for Villa 7 (1971–1975)

open access articleIn 1971, after more than a decade of national and municipal policies aimed at the top-down removal of shantytowns, the Buenos Aires City Council approved the Plan Piloto para la Relocalización de Villa 7 (Pilot Plan for the Relocation of Shantytown 7; 1971–1975, referred to as the Pilot Plan hereinafter). This particular plan, which resulted in the construction of the housing complex, Barrio Justo Suárez, endures in the collective memory of Argentines as a landmark project regarding grassroots participation in state housing initiatives addressed at shantytowns. Emerging from a context of a housing shortage for the growing urban poor and intense popular mobilizations during the transition to democracy, the authors of the Pilot Plan sought to empower shantytown residents in novel ways by: 1) maintaining the shantytown’s location as opposed to eradication schemes that relocated the residents elsewhere, 2) formally employing some of the residents for the stage of construction, as opposed to “self-help” housing projects in which the residents contributed with unpaid labor, and 3) including them in the urban and architectural design of the of the new housing. This paper will examine the context in which the Pilot Plan was conceived of as a way of re-assessing the roles of the state, the user, and housing-related professionals, often seen as antagonistic. The paper argues that residents’ fair participation and state intervention in housing schemes are not necessarily incompatible, and can function in specific social and political contexts through multiactor proposals backed by a political will that prioritizes grassroots agency

Morphology of Blends with Cross-Linked PMMA Microgels and Linear PMMA Chains

The present work investigates PMMA colloids in a polymer matrix of linear chains as a simple and suitable system for complex nanocomposites. The investigation was based on SANS experiments, which were enabled by the use of deuterated colloids immersed in a matrix of linear hydrogenated chains. Cross-linked deuterated PMMA-colloids were synthesized with two different sizes (70 and 140 nm) by means of the surfactant-free emulsion polymerization method and the swelling behavior adjusted by varying the amount of added cross-linker (1.5 and 15.0 mol-%) at each size respectively. Colloid–polymer blends were prepared from colloid–polymer solutions. SANS experiments on these blends consistently revealed that colloids with a low cross-linking density could be homogeneously distributed throughout the matrix of linear chains. Fits with model form factors indicated the structure of fuzzy spheres for these molecularly dispersed microgels, which are slightly swollen with respect to their size and shape in H2O. Contrary to this, colloids with a high cross-linking density form aggregates in the blends. Despite this aggregation, we succeeded to unravel the shape and the size of single colloids by preparation of colloid–polymer blends where the colloid component is a binary mixture of deuterated and hydrogenated colloids both with a high cross-linking density. SANS on the latter blends suggested a core–shell particle in a lattice cell of an aggregate