The MESSENGER Spacecraft Leary, James C; Conde, Richard F; Dakermanji, George ...
Space science reviews,
8/2007, Letnik:
131, Številka:
1-4
Journal Article
Recenzirano
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was designed and constructed to withstand the harsh environments associated with achieving and operating in ...Mercury orbit. The system can be divided into eight subsystems: structures and mechanisms (e.g., the composite core structure, aluminum launch vehicle adapter, and deployables), propulsion (e.g., the state-of-the-art titanium fuel tanks, thruster modules, and associated plumbing), thermal (e.g., the ceramic-cloth sunshade, heaters, and radiators), power (e.g., solar arrays, battery, and controlling electronics), avionics (e.g., the processors, solid-state recorder, and data handling electronics), software (e.g., processor-supported code that performs commanding, data handling, and spacecraft control), guidance and control (e.g., attitude sensors including star cameras and Sun sensors integrated with controllers including reaction wheels), radio frequency telecommunications (e.g., the spacecraft antenna suites and supporting electronics), and payload (e.g., the science instruments and supporting processors). This system architecture went through an extensive (nearly four-year) development and testing effort that provided the team with confidence that all mission goals will be achieved.
A Mercury orbiter mission is challenging from thermal and mass perspectives. The Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) mission overcomes these challenges while ...avoiding esoteric technologies by using an innovative approach with commonly available materials, minimal moving parts, and maximum heritage. This approach yields a spacecraft with good margins in all categories and low technical risk. The key concepts are a ceramic-cloth sunshade, an integrated lightweight structure and high- performance propulsion system, and a solar array incorporating optical solar reflectors (OSRs). The sunshade maintains the spacecraft at room temperature. The integrated structure and propulsion system provides ample mass margin. The solar array with OSRs, which has already undergone significant testing, provides thermal margin even if the panels are inadvertently pointed directly at the Sun at 0.3 AU.
0.3
AU
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Mission velocity change requirements for the Near Earth Asteroid Rendezvous (NEAR) mission dictated the use of regulated dual-mode propulsion and a lightweight, stiff composite structure. Fixed solar ...array and high-gain antenna locations, combined with mission trajectory constraints, dictated an unusual thruster arrangement. A unique sequencing of individual tank outlet latch valves will maintain the spacecraft y and z center of mass within +/- 2 mm during expulsion of the 315-kg propellant load. The use of flight-proven components, a sequential protoflight test philosophy, and a small integrated product team resulted in the successful development, manufacture, testing, and integration of the propulsion system into the spacecraft in just 16 months. In-flight performance to date has been very close to preflight predictions. (Author)
On 17 February, 1996, a Delta-2 rocket placed NASA’s Near-Earth Asteroid Rendezvous (NEAR) spacecraft into a 2-year ΔVEGA trajectory that will rendezvous with the large near-Earth asteroid, 433 Eros ...in early January 1999. This paper discusses the strategy for performing NEAR’s two large deterministic ΔVs, the Deep Space Maneuver (DSM; 269 m/s) 4 months after aphelion of the initial 2-year orbit and the rendezvous (RND; total 971 m/s) with Eros. The DSM was performed flawlessly on 3 July, 1997, 6 days after NEAR’s flyby of the main-belt asteroid 253 Mathilde. But NEAR could have still gone into orbit about Eros even if there had been a delay of 8 weeks in performing the DSM. The RND maneuver will be much more time-critical than the DSM. The rendezvous will be split into four burns of decreasing size, the error for each of which will be successively decreased. The design can accommodate one-day and two-day delays. After that, NEAR will fly past Eros, necessitating longer delays and higher ΔV costs to orbit the asteroid. A strategy is shown that will allow the full Eros orbital phase to be performed with delays as long as 40 days in performing the first large rendezvous burn. If in the unlikely event the delay is even longer, NEAR could be aimed to swing by the Earth in January 2003, and from there it could encounter 4 Vesta and other interesting objects.
The MESSENGER Spacecraft LEARY, James C; CONDE, Richard F; MIRANTES, Mary A ...
Space science reviews,
2007, Letnik:
131, Številka:
1-4
Journal Article
Women with metastatic breast cancer face a wide range of medical, practical, and emotional challenges that impact their quality of life. Research to date, however, has not focused on the ...quality‐of‐life concerns of metastatic breast cancer patients with significant distress. The present study examined a range of concerns among distressed metastatic breast cancer patients, including physical and emotional distress, social functioning, and existential issues. Forty‐four distressed women with metastatic breast cancer wrote their deepest thoughts and feelings regarding their illness. These essays were thematically analyzed for effects of the illness on quality of life. Three themes were identified in patients' essays. First, metastatic breast cancer and its treatment may result in a number of quality‐of‐life concerns, including physical symptom burden, emotional distress, body image disturbance, and disrupted daily activities. Second, social constraints on disclosure of cancer‐related concerns may exacerbate patients' distress. Third, many women experience a heightened awareness of life's brevity and search for meaning in their cancer experience. Results highlight a range of quality‐of‐life concerns following a metastatic breast cancer diagnosis and suggest that addressing social constraints on cancer‐related disclosure and the search for meaning may improve patients' psychological adjustment.
Women with metastatic breast cancer and significant psychological distress (N = 87) were assigned randomly to engage in four home-based sessions of expressive writing or neutral writing. Women in the ...expressive writing group wrote about their deepest thoughts and feelings regarding their cancer, whereas women in the neutral writing group wrote about their daily activities in a factual manner. No statistically significant group differences in existential and psychological well-being, fatigue and sleep quality were found at 8-weeks post-writing. However, the expressive writing group reported significantly greater use of mental health services during the study than the neutral writing group (55% vs. 26%, respectively; p < 0.05). Findings suggest that expressive writing may improve the uptake of mental health services among distressed cancer patients, but is not broadly effective as a psychotherapeutic intervention.
The MESSENGER Spacecraft Leary, James C.; Conde, Richard F.; Dakermanji, George ...
The Messenger Mission to Mercury,
11/2007
Book Chapter
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was designed and constructed to withstand the harsh environments associated with achieving and operating in ...Mercury orbit. The system can be divided into eight subsystems: structures and mechanisms (e.g., the composite core structure, aluminum launch vehicle adapter, and deployables), propulsion (e.g., the state-of-the-art titanium fuel tanks, thruster modules, and associated plumbing), thermal (e.g., the ceramic-cloth sunshade, heaters, and radiators), power (e.g., solar arrays, battery, and controlling electronics), avionics (e.g., the processors, solid-state recorder, and data handling electronics), software (e.g., processor-supported code that performs commanding, data handling, and spacecraft control), guidance and control (e.g., attitude sensors including star cameras and Sun sensors integrated with controllers including reaction wheels), radio frequency telecommunications (e.g., the spacecraft antenna suites and supporting electronics), and payload (e.g., the science instruments and supporting processors). This system architecture went through an extensive (nearly four-year) development and testing effort that provided the team with confidence that all mission goals will be achieved.
Hybrid analogs of the cholecystokinin A (CCK-A) receptor selective tetrapeptide agonist Boc-Trp-Lys(Tac)-Asp-MePhe-NH2 (1,A-71623) and the CCK-B receptor selective antagonists PD-135118 (2) and ...CI-988 (3) were prepared. Incorporation of the Lys(Tac) side chain into 2 produced a moderately potent antagonist of CCK-8 in the isolated guinea pig gallbladder (GPGB). Incorporation of the Lys(Tac) side chain into 3 produced the novel agonist analog 7 (EC50 = 28 nM in the GPGB) with excellent affinity for both human CCK-A (IC50 = 12 nM) and CCK-B (IC50 = 17 nM) receptors. Analog 7 was a full agonist (EC50 = 3.5 nM) for calcium mobilization on CHO-K1 cells expressing hCCK-A receptors but a partial agonist on CHO-K1 cells expressing hCCK-B receptors, eliciting a weak agonist response (EC50 = 2800 nM) and antagonizing CCK-8-induced calcium mobilization (KB = 20 nM). Despite this unusual in vitro profile, analog 7 was a potent anorectic agent in rats (ED50 = 30 nmol/kg) following intraperitoneal administration.
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