Pressure Profile Systems (United States)

Due to concern over frequent loss-of-track events common to several near-Earth NASA spacecraft employing a popular charge-coupled device (CCD) star tracker, an on-orbit experiment was conducted to determine and then correct its root cause. Similar to CCD trackers from other manufacturers, the Ball Aerospace CT601 star tracker has consistently experienced upsets while operating in both the polar regions during active solar periods and the Earth's trapped radiation belts. Using NASA's Wide-field Infrared Explorer (WIRE) spacecraft, high frequency raw pixel data from the CT601 tracker was obtained during multiple loss-of-track events occurring over a four-week period. Experimental data indicated that loss-of-track events were precipitated by the impact of high-energy particles at the start of a read cycle on the pixel region used for a bias offset calculation. A corrective software patch was then written and uploaded to the spacecraft. The patch delays the bias offset update for one read cycle if new and past values are inconsistent. Additional high rate raw pixel data was then collected over several weeks. Tracker anomalies were eliminated, even though the data showed the occurrence of several high-energy particle impact events. The patch has since been implemented successfully on several other NASA missions.

Cold silicon piezoresistive strain gauge pressure sensors have several advantages over the conventional pressure measuring devices/systems used in cryogenics. A cryogenic pressure sensor calibration facility has been set up at Pressure Systems, Inc. for calibrating cryogenic pressure sensors in the temperature range 1.5 – 400 K. This paper presents a brief review of this calibration facility together with the low temperature characteristics of the cryogenic piezoresistive pressure sensors. The pressure sensors calibrated so far include 202 k Pa absolute (30 psia), 202 k Pa differential (30 psid) and 1013 k Pa absolute (150 psia) range devices. These calibrations are linear and are repeatable to within +/− 0.1% and +/− 0.5% full scale outputs for 202 k Pa and 1013 k Pa range pressure sensors respectively.

The purpose of this study was to determine cardiovascular reactions after the administration of a potent narcotic analgesic, such as fentanyl, in increasing dosages of 0.0025 to 0.16 mg./kg. In addition, comparison was made with meperidine in dosages from 2.5 to 20 mg./kg. The action of a narcotic antagonist (0.4 mg./kg. of naloxone) given in sequence to the analgesic was ascertained also. The data obtained indicate: 1. Increase in LV dP/dt max* was directly proportional to the dose of fentanyl over a low concentration range (0.0025 to 0.03 mg./kg.). 2. Increasing dosages of fentanyl caused a decrease in myocardial oxygen consumption (maximum 30 percent), pressure time index (TTI), and coronary sinus blood flow. 3. High dosages of fentanyl (0.03 to 0.16 mg./kg.) did not affect LV dP/dt max, left ventricular pressure, left ventricular end-diastolic pressure, and central aortic blood pressure. 4. Increasing dosages of fentanyl produced a proportionately greater decrease in mean peripheral blood pressure (maximum 40 percent) and heart rate (maximum 50 percent). Succeeding injection of the same doses had little effect on the two physiologic values, however, suggesting the development of tachyphylaxis. 5. Naloxone given after fentanyl increased all measured values. 6. Meperidine, even in low doses of 2.5 mg./kg., had a depressant effect on the cardiovascular system, particularly in regard to left ventricular pressure. 7. Naloxone alone, up to 5.6 mg./kg., had no effect on the cardiovascular system. The results suggest that sequential analgesia, using in sequence high doses of fentanyl as the sole anesthetic agent and naloxone as the antagonist at the end of the operation, has no depressant effect on the cardiovascular system.