Spin rate estimation of sounding rockets using GPS wind-up

Carrier phase wind-up is a well-known effect that arises from the relative rotation between a transmitting and receiving antenna. In GPS measurements at L1 frequency, this effect translates into an error of 19.029 cm per full relative rotation of antennas. Since this effect is independent of the satellite elevation for pure rotation about the antenna boresight axis, it is usually absorbed by the clock estimation in navigation algorithms. Therefore, the impact of wind-up is usually neglected for applications that do not require accuracies to the cm level like RTK. However, in receiving platforms with high rotation rate, the accumulated wind-up value can be important and actually be larger than receiver noise or even ionospheric variations. Therefore, in such scenarios, the wind-up contribution can be isolated and used as a source of information to compute the spin rate of such platforms using an appropriate combination of GPS observables. This work shows some results of a coarse, yet simple, approach to monitor the rotation angle and spin-rate of spin stabilized sounding rockets flown by DLR.     

The ionosphere: effects,GPS modeling and the benefits for space geodetic techniques

The main goal of this paper is to provide a summary of our current knowledge of the ionosphere as it relates to space geodetic techniques, especially the most informative technology, global navigation satellite systems (GNSS), specifically the fully deployed and operational global positioning system (GPS). As such, the main relevant modeling points are discussed, and the corresponding results of ionospheric monitoring are related, which were mostly computed using GPS data and based on the direct experience of the authors. We address various phenomena such as horizontal and vertical ionospheric morphology in quiet conditions, traveling ionospheric disturbances, solar flares, ionospheric storms and scintillation. Finally, we also tackle the question of how improved knowledge of ionospheric conditions, especially in terms of an accurate understanding of the distribution of free electrons, can improve space geodetic techniques at different levels, such as higher-order ionospheric effects, precise GNSS navigation, single-antenna GNSS orientation and real-time GNSS meteorology.     

Impacts of macroalgal spores on the dynamics of adult macroalgae in a eutrophic estuary: high versus low hydrodynamic seasons and long-term simulations for global warming scenarios

A model describing macroalgal early life stages and adult dynamics was used to quantify the effects of non-adult forms on the productivity of adult macroalgae in a eutrophic estuary. Predictions indicate that during years with mild winters and low rainfall, spring blooms will occur at the expense of the growth and reproduction of overwintering adults and without the contribution of the spore bank. In these circumstances, there is a positive correlation between the intensity of the blooms and the biomass of overwintering adults until a maximum threshold value. On the contrary, in years with high rainfall and low or inexistent biomass of overwintering adults, the onset of adult’s growth depends on the biomass of viable dormant spores, the growing season occurs later and adult productivity is very limited. Long-term predictions for climate change scenarios suggest that, in general, global warming will have adverse affects on Ulva intestinalis productivity, with the adults being more affected than the early life stages.     

Stress Field Estimations for Colima Volcano, Mexico, Based on Seismic Data

 For first time, during 1991, seismic activity was recorded during an eruption at Colima volcano. We analyze these data to obtain a stress pattern using a composite focal mechanism technique. From the analysis of regional seismicity, the Tamazula Fault and the Armeria River appear as active features and the dip of the slab east of the Jalisco Block is approximately 12°. Southwest of Colima volcano a vertical alignment of seismic events was observed. We estimate five different composite focal mechanism solutions from our data set, which indicate a change of the stress field at the volcano after the 1991 eruption. These solutions suggest that the stress field in the volcanic edifice was controlled by stresses related to the emplacement of magma superimposed on the regional stress field. No evidence of active local faults in the volcanic edifice was found. We propose a model for the eruptive process that involves tilting of the volcanic edifice. Received: 15 October 1995 / Accepted: 26 October 1998     

Persistent organic pollutants and histological lesions in Mayan catfish Ariopsis assimilis from the Bay of Chetumal, Mexico

Livers of catfish (Ariopsis assimilis) from the Bay of Chetumal were analyzed for organochlorine compounds and hydrocarbons as part of a study to diagnose the environmental health of the Bay after a catfish mass mortality that occurred in 1996. The presence of histological lesions in several organs of the fish as result of chemical exposure was also evaluated. The concentrations of organic pollutants found in the Bay may be considered high if compared to the levels reported for sites affected by chemical pollution. High prevalences of cellular alteration histopathologies were found in liver, including hepatic tumors. The presence of some lesions may be related statistically to environmental pollution in the Bay, specially with chlorinated compounds.     

A comparative study of geothermal and meteorological records of climate change in Kamchatka

To reconstruct the recent climate history in Kamchatka, a series of repeated precise temperature logs were performed in a number of boreholes located in a broad east-west strip (between 52 and 54°N) in the central part of Kamchatka west of Petropavlovsk-Kamchatski. Within three years more than 30 temperature logs were performed in 10 holes (one up to six logs per hole) to the depth of up to 400 metres. Measured temperature gradients varied in a broad interval 0 to 60 mK/m and in some holes a sizeable variation in the subsurface temperatures due to advective heat transport by underground water was observed. Measured data were compared with older temperature profiles obtained in the early eighties by Sugrobov and Yanovsky (1993). Even when older data are of poorer precision (accuracy of about 0.1 K), they presented valuable information of the subsurface temperature conditions existing 20–25 years ago. Borehole observations and the inverted ground surface temperature histories (GSTHs) used for the paleoclimate reconstruction were complemented with a detailed survey of meteorological data. Namely, the long-term surface air temperature (SAT) and precipitation records from Petropavlovsk station (in operation since 1890) were used together with similar data from a number of local subsidiary meteo-stations operating in Central Kamchatka since 1950. Regardless of extreme complexity of the local meteorological/climate conditions, diversity of borehole sites and calibration of measuring devices used during the whole campaign, the results of the climate reconstruction supported a general warming of about 1 K characteristic for the 20th century, which followed an inexpressive cooler period typical for the most of the 19th century. In the last three to four decades the warming rate has been locally increasing up to 0.02 K/year. It was also shown that the snow cover played a dominant role in the penetration of the climate “signal” to depth and could considerably smooth down the subsurface response to the changes occurred on the surface.     

Food gardens as important elements of urban agriculture: Spatio-developmental trends and future prospects for urban gardening in Czechia

The main research goals of the article are to explain the historical context of urban food gardens in Czechia, to describe the current spatial pattern of allotment gardens, and to introduce and analyse recent trends in urban gardening. The main method for achieving the first goal was a literature study. For the second goal, geographical mapping and analysis of data relating to the spatial distribution of allotment gardens were used. For the third goal, mapping together with analysis of semi-structured interviews carried out in community gardens in Prague were used. The analysis showed a strong tradition of urban agriculture and urban food gardening activities in Czechia. Both allotment gardens and newly emerged community gardens were concentrated mainly in the biggest cities and in areas with a rich industrial and mining tradition. This finding supports the significance of gardening as an important element of urban agriculture. However, uncertainty regarding land tenure and long-term sustainability were among the greatest obstacles for the future of allotment and community gardens. The authors’ main recommendations are that urban agriculture should be included as primary land use in sustainable planning and there should be broader community involvement in planning and decision-making processes.