Reflex feed system for dual frequency antenna with frequency cutoff means

A reflex feed system is described for a dual frequency antenna such as one which transmits and receives both S and X band signals. The dichroic plate, normally employed for directing X band radiation away from the X band horn, is replaced by a flange about the opening of the X band horn

Microwave component time delays for the 70-meter antennas

The X-band feed assemblies in the 64 meter antennas were redesigned to accommodate the upgrading to 70 meters and the associated surface reshaping. To maintain time delay data logs, new calculations were made of the microwave component delays for the XRO Mod IV X-band (8.4 to 8.45 GHz) feed assembly that was installed at DSS-63, and will soon be implemented at DSS-43 and DSS-14

Compound-taper feedhorn for the DSN 70-meter antennas

A novel X-band feedhorn was designed for the Deep Space Network (DSN) 70-meter antennas. The feedhorn is a compound-taper structure consisting of a corrugated flared section and a corrugated straight section. This feedhorn is designed to closely initiate the characteristics of the standard feedhorn, while providing the proper phase center location, without adding any significant loss to the system. The use of the existing feedhorn and the ease of manufacturing the corrugated straight section have resulted in major overall cost savings

Waveguide cooling system

An improved system is described for cooling high power waveguides by the use of cooling ducts extending along the waveguide, which minimizes hot spots at the flanges where waveguide sections are connected together. The cooling duct extends along substantially the full length of the waveguide section, and each flange at the end of the section has a through hole with an inner end connected to the duct and an opposite end that can be aligned with a flange hole in another waveguide section. Earth flange is formed with a drainage groove in its face, between the through hole and the waveguide conduit to prevent leakage of cooling fluid into the waveguide. The ducts have narrowed sections immediately adjacent to the flanges to provide room for the installation of fasteners closely around the waveguide channel

The Impact of Nitrite on Aerobic Growth of Paracoccus denitrificans PD1222

The effect of nitrite stress induced in Paracoccus denitrificans PD1222 was examined using additions of sodium nitrite to an aerobic bacterial culture. Nitrite generates a strong stress response in P. denitrificans, causing growth inhibition. This is dependent on both the concentration of nitrite present and the pH. The pH dependent effect of nitrite growth inhibition is likely a result of nitrite and free nitrous acid (FNA; pKa = 3.16) and subsequent reactive nitrogen oxides, generated from the intracellular passage of FNA into P. denitrificans. A flavohemoglobin (fhb; Pd1689) and its associated NsrR family, transcriptional regulator (Pd1690), were transcribed above a ≥2 fold expression filter (p ≤ 0.05) at 95% significance in qRT-PCR and a type II microarray transcriptional analysis at 12.5 mM nitrite in batch culture. Additionally, >25 fold expression of the flavohemoglobin was confirmed by qRT-PCR in continuous culture with nitrite. A deletion mutant determined fhb to be involved in conveying nitrite resistance at high nitrite concentrations and is linked to a stimulation of biomass generated by the presence of nitrite. The cytochrome ba3 oxidase was found to be associated with nitrite in transcriptional analysis, suggesting the uncoupling of the protonmotive force caused by the transport of FNA across the membrane, and subsequent dissociation in the cytoplasm were reduced by a method of counterbalance. No nitrate accumulation was seen and nitrous oxide levels were above that observed for atmospheric background levels. The microarray analysis was used to confirm that in batch growth at 12.5 mM nitrite addition, P. denitrificans shows an overall stress response associated with protein, DNA and lipid repair, with the addition of fhb detoxification and action of the cytochrome ba3 oxidase. It is therefore suggested that nitrite presents a pHdependent stress response in P. denitrificans, likely due to the production of associated reactive nitrogen species such as NO from the internalisation of FNA and the uncoupling of the protonmotive force

A Ka-band (32 GHz) beacon link experiment (KABLE) with Mars Observer

A proposal for a Ka-Band (32 GHz) Link Experiment (KABLE) with the Mars Observer mission was submitted to NASA. The experiment will rely on the fourth harmonic of the spacecraft X-band transmitter to generate a 33.6 GHz signal. The experiment will rely also on the Deep Space Network (DSN) receiving station equipped to simultaneously receive X- and Ka-band signals. The experiment will accurately measure the spacecraft-to-Earth telecommunication link performance at Ka-band and X-band (8.4 GHz)