Papers by Ricardo Mendoza
2007 IEEE Aerospace Conference, 2007
NASA's mars reconnaissance orbit... more NASA's mars reconnaissance orbiter (MRO) was launched on August 12, 2005 and was inserted into Mars orbit successfully on March 10, 2006. From September 2005 through January 2006, the Ka-band signal from the spacecraft was tracked several times by NASA's deep space network (DSN). During these tracks a number of Ka-band functions for both the spacecraft and the ground systems
The X-band (8.41 GHz) frequency currently used for deep space telecommunications is too narrow (5... more The X-band (8.41 GHz) frequency currently used for deep space telecommunications is too narrow (50 MHz) to support future high rate missions. Because of this NASA has decided to transition to Ka-band (32 GHz) frequencies. As weather effects cause much larger fluctuations on Ka-band than on X-band, the traditional method of using a few dBs of margin to cover these fluctuations is wasteful of power for Ka-band; therefore, a different operations concept is needed for Ka-band links. As part of the development of the operations concept for Ka-band, NASA has implemented a fully functioning Ka-band communications suite on its Mars Reconnaissance Orbiter (MRO). This suite will be used during the primary science phase to develop and refine the Ka-band operations concept for deep space missions. In order to test the functional readiness of the spacecraft and the Deep Space Network's (DSN) readiness to support the demonstration activities a series of passes over DSN 34-m Beam Waveguide (BWG) antennas were scheduled during the cruise phase of the mission. MRO was launched on August 12, 2005 from Kennedy Space Center, Cape Canaveral, Florida, USA and went into Mars Orbit on March 10, 2006. A total of ten telemetry demonstration and one high gain antenna (HGA) calibration passes were allocated to the Ka-band demonstration. Furthermore, a number of "shadow" passes were also scheduled where, during a regular MRO track over a Ka-band capable antenna, Ka-band was identically configured as the X-band and tracked by the station. In addition, nine Ka-band delta differential one way ranging (∆DOR) passes were scheduled. During these passes, the spacecraft and the ground system were put through their respective paces. Among the highlights of these was setting a single day record for data return from a deep space spacecraft (133 Gbits) achieved during one 10-hour pass; achieving the highest data rate ever from a planetary mission (6 Mbps) and successfully demonstrating Ka-band DDOR. In addition, DSN performed well. However, there are concerns with the active pointing of the Ka-band antennas as well as delivery of the monitor data from the stations. The spacecraft also presented challenges not normally associated with planetary missions mostly because of its very high equivalent isotropic radiated power (EIRP). This caused problems in accurately evaluating the in-flight EIRP of the spacecraft which led to difficulties evaluating the quality of the HGA calibration data. These led to the development of additional measurement techniques that could be used for future high-power deep space missions.
NASA's mars reconnaissance orbiter (MRO) was launched on August 12, 2005 and was inserted into Ma... more NASA's mars reconnaissance orbiter (MRO) was launched on August 12, 2005 and was inserted into Mars orbit successfully on March 10, 2006. From September 2005 through January 2006, the Ka-band signal from the spacecraft was tracked several times by NASA's deep space network (DSN). During these tracks a number of Ka-band functions for both the spacecraft and the ground systems were tested. These tests were performed to assess the readiness of the ground system and spacecraft to support Ka-band demonstration activities during MRO's primary science phase (PSP). As a result of these tests a number of important lessons were learned regarding the performance of the Ka-band link and the performance of the ground equipment. This paper presents the performance of the ground antenna pointing, delta differential one-way ranging (DeltaDOR) performance and the telemetry performance of the Ka-band link. These results indicate that the extra effort for pointing calibration of the ground antennas at Ka-band is extremely useful; Ka-band shows potential for improved DeltaDOR performance and the models for Ka-band performance of the ground station microwave noise temperature are very accurate.
Human Biology, 2006
Two hundred seventeen male subjects from Costa Rica, Mexico, and the Hispanic population of the s... more Two hundred seventeen male subjects from Costa Rica, Mexico, and the Hispanic population of the southwestern United States were studied. Twelve Y-chromosome STRs and the HVSI sequence of the mtDNA were analyzed to describe their genetic structure and to compare maternal and paternal lineages. All subjects are part of two NIMH-funded studies to localize schizophrenia susceptibility genes in Hispanic populations of Mexican and Central American ancestry. We showed that these three populations are similar in their internal genetic characteristics, as revealed by analyses of mtDNA and Y-chromosome STR diversity. These populations are related through their maternal lineage in a stronger way than through their paternal lineage, because a higher number of shared haplotypes and polymorphisms are seen in the mtDNA (compared to Y-chromosome STRs). These results provide evidence of previous contact between the three populations and shared histories. An analysis of molecular variance revealed no genetic differentiation for the mtDNA for the three populations, but differentiation was detected in the Y-chromosome STRs. Genetic distance analysis showed that the three populations are closely related, probably as a result of migration between close neighbors, as indicated by shared haplotypes and their demographic histories. This relationship could be an important common feature for genetic studies in Latin American and Hispanic populations.
American Journal of Medical Genetics Part B-neuropsychiatric Genetics, 2009
Methionine sulfoxide reductase (MSRA) is an antioxidant enzyme implicated in protection against o... more Methionine sulfoxide reductase (MSRA) is an antioxidant enzyme implicated in protection against oxidative stress and protein maintenance. We have previously reported the association of marker D8S542, located within the MSRA gene, with schizophrenia in the Central Valley of Costa Rica (CVCR). By performing fine mapping analysis, we have now identified a potential three-marker at risk haplotype within MSRA in the same CVCR sample, with a global P-value slightly above nominal significance (P = 0.0526). By sequencing the MSRA gene in individuals carrying this haplotype, we identified a novel 4-base pair deletion 1,792 bases upstream of the MSRA transcription start site. This deletion was significantly under-transmitted to schizophrenia patients in the CVCR sample (P = 0.0292) using FBAT, and this was replicated in a large independent sample of 321 schizophrenia families from the Hispanic population (P = 0.0367). These findings suggest a protective effect of the deletion against schizophrenia. Further, MSRA mRNA levels were significantly lower in lymphoblastoid cell lines of individuals homozygous for the deletion compared to carriers of the normal allele (P = 0.0135), although significance was only evident when genotypes were collapsed. This suggests that the deleted sequence may play a role in regulating MSRA expression. In conclusion, this work points towards MSRA as a novel schizophrenia candidate gene. Further studies into the mechanisms by which MSRA is involved in schizophrenia pathophysiology may shed light into the biological underpinnings of this disorder. © 2008 Wiley-Liss, Inc.
Human biology, 2007
Two hundred seventeen male subjects from Costa Rica, Mexico, and the Hispanic population of the s... more Two hundred seventeen male subjects from Costa Rica, Mexico, and the Hispanic population of the southwestern United States were studied. Twelve Y-chromosome STRs and the HVSI sequence of the mtDNA were analyzed to describe their genetic structure and to compare maternal and paternal lineages. All subjects are part of two NIMH-funded studies to localize schizophrenia susceptibility genes in Hispanic populations of Mexican and Central American ancestry. We showed that these three populations are similar in their internal genetic characteristics, as revealed by analyses of mtDNA and Y-chromosome STR diversity. These populations are related through their maternal lineage in a stronger way than through their paternal lineage, because a higher number of shared haplotypes and polymorphisms are seen in the mtDNA (compared to Y-chromosome STRs). These results provide evidence of previous contact between the three populations and shared histories. An analysis of molecular variance revealed no genetic differentiation for the mtDNA for the three populations, but differentiation was detected in the Y-chromosome STRs. Genetic distance analysis showed that the three populations are closely related, probably as a result of migration between close neighbors, as indicated by shared haplotypes and their demographic histories. This relationship could be an important common feature for genetic studies in Latin American and Hispanic populations.
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Papers by Ricardo Mendoza