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NASA NTRS1996

Calcium Balance in Mature Rats Exposed to a Space Flight Model

Negative calcium balances are seen in humans during spaceflight and bed rest, an analog of space flight. Due to the infrequency and costliness of space flight and the difficulties, cost, and restraints in using invasive procedures in bed rest studies, several ground based animal models of space flight have been employed. The most useful and well developed of these models is hind limb unloading in the rat. In this model the hind limbs are non-weight bearing (unloaded) but still mobile; there is a cephalad fluid shift similar to that seen in astronauts in flight; the animals are able to feed, groom and locomote using their front limbs; the procedure is reversible; and, importantly, the model has been validated by comparison to space flight. Several laboratories have studied calcium balance using rats in hind limb unweighting. Roer and Dillaman used young male rats to study calcium balance in this model for 25 days. They found no differences in dietary calcium intake, percent calcium absorption, urinary and fecal excretion, hence indicating no differences in calcium balance between control and unloaded rats. In another study, employing 120 day old females, rats' hind limbs were unloaded for 28 days. While negative calcium balances were observed during a 25 day recovery period no balance measurements were possible during unweighting since the researchers did not employ appropriate metabolic cages. In a recent study from this laboratory, using 200 g rats in the space flight model for two weeks, we found depressed intestinal calcium absorption and increased fecal calcium excretion (indicating less positive calcium balances) and lower circulating 1,25-dihydroxyvitamin D. The above studies indicate that there remains a dearth of information on calcium balance during the hind limb unloading rat space flight model, especially in mature rats, whose use is a better model for planned manned space flight than juvenile or growing animals. With the aid of a newly designed metabolic cage developed in our laboratory it is now possible to accurately measure urinary and fecal calcium excretions in this space flight model. The purpose of this study, then, was to extend and enlarge our previous findings viz: to measure calcium balances in mature rats exposed to a space flight model.

Wolinsky, Ira↗

NASA NTRS1998

On the Maturity of Lunar Regolith

Spectral reflectance properties of the lunar regolith change as the regolith "matures" with exposure to the space environment; a regolith composed of fragments from freshly disaggregated rock is lighter, is less red, and has more spectral contrast than the same regolith after it has received lengthy exposure to the solar wind, cosmic charged particles, and micrometeorite impact. In this work we discuss some aspects of lunar regolith maturity based on the study of Apollo regolith samples that may be important to interpretation of data obtained remotely.

Korotev, Randy L.↗

NASA NTRS1996

Calcium Balance in Mature Rats Exposed to a Space Flight Model

Depressed intestinal calcium absorption (Ca abs.) and lower circulating 1,25-dihydroxyvitamin D (1,25-D) are associated with less positive calcium balance in young 200 g rats exposed to skeletal unloading by hind-limb suspension than controls (C) . To determine the effect of the space flight model on calcium balance in mature rats, we exposed 6 mo. old males weighing 492 +/- 12g to the model for 4 weeks (S) and compared Ca in the diet, urine, feces and 1,25-D in S and C. Rats were fed diets containing sufficient Ca to satisfy metabolic needs, but not to cause deficiency (0.1%). At the end of 4 weeks, there was a 5 percent weight loss in S, but not in C; and no differences in dietary, urine (UCa) or fecal Ca (FCa) in S and C. Net Ca abs. (0.1 vs 2.7 %), 1,25-D (50 +/- 16 vs 47 +/- 14 pg/ml) and Ca balances (-1.8 +/- 4 vs -1.0 +/- 2.9 mg/d) were similar in C and S. UCa loss was added to the model by inducing calciuria with 8% salt diets (HiNa). A 4-fold increase in UCa in C and S was transiently higher in S than C after 1 week. After 4 weeks, loss in BW was greater in S than C, Ca abs was higher in C than S (32 +/- 10 vs 3.5 +/- 16%, p less than .05), 1,25-D greater in S than C (98 +/- 15 vs 79 +/- 14 pg/ml p less than .05) and Ca balance less in S than C (-5.2 +/- 4 vs -1.7 +/- 2 mg/d, p less than .05). Ca balance in the mature rat is unaffected by the space flight model unless calciuria intervenes and reveals the failure of the intestine to enhance Ca abs. and compensate for UCa loss.

Navidi, Meena↗

NASA NTRS2002

Rapid Maturation of Edge Sensor Technology and Potential Application in Large Space Telescopes with Segmented Primary Mirrors

This paper explores the history and results of the last two year's efforts to transition inductive edge sensor technology from Technology Readiness Level 2 to Technology Readiness Level 6. Both technical and programmatic challenges were overcome in the design, fabrication, test, and installation of over a thousand sensors making up the Segment Alignment Maintenance System (SAMs) for the 91 segment, 9.2-meter. Hobby Eberly Telescope (HET). The integration of these sensors with the control system will be discussed along with serendipitous leverage they provided for both initialization alignment and operational maintenance. The experience gained important insights into the fundamental motion mechanics of large segmented mirrors, the relative importance of the variance sources of misalignment errors, the efficient conduct of a program to mature the technology to the higher levels. Unanticipated factors required the team to develop new implementation strategies for the edge sensor information which enabled major segmented mirror controller design simplifications. The resulting increase in the science efficiency of HET will be shown. Finally, the on-going effort to complete the maturation of inductive edge sensor by delivering space qualified versions for future IR (infrared radiation) space telescopes.

Montgomery, Edward E., IV↗

NASA NTRS2003

Hindlimb unloading has a greater effect on cortical compared with cancellous bone in mature female rats

This study was designed to determine the effects of 28 days of hindlimb unloading (HU) on the mature female rat skeleton. In vivo proximal tibia bone mineral density and geometry of HU and cage control (CC) rats were measured with peripheral quantitative computed tomography (pQCT) on days 0 and 28. Postmortem pQCT, histomorphometry, and mechanical testing were performed on tibiae and femora. After 28 days, HU animals had significantly higher daily food consumption (+39%) and lower serum estradiol levels (-49%, P = 0.079) compared with CC. Proximal tibia bone mineral content and cortical bone area significantly declined over 28 days in HU animals (-4.0 and 4.8%, respectively), whereas total and cancellous bone mineral densities were unchanged. HU animals had lower cortical bone formation rates and mineralizing surface at tibial midshaft, whereas differences in similar properties were not detected in cancellous bone of the distal femur. These results suggest that cortical bone, rather than cancellous bone, is more prominently affected by unloading in skeletally mature retired breeder female rats.

NASA Discipline Musculoskeletal↗

NASA NTRS2002

Site- and compartment-specific changes in bone with hindlimb unloading in mature adult rats

The purpose of this study was to examine site- and compartment-specific changes in bone induced by hindlimb unloading (HU) in the mature adult male rat (6 months old). Tibiae, femora, and humeri were removed after 14, 21, and 28 days of HU for determination of bone mineral density (BMD) and geometry by peripheral quantitative computed tomography (pQCT), mechanical properties, and bone formation rate (BFR), and compared with baseline (0 day) and aging (28 day) controls. HU resulted in 20%-21% declines in cancellous BMD at the proximal tibia and femoral neck after 28 day HU vs. 0 day controls (CON). Cortical shell BMD at these sites was greater (by 4%-6%) in both 28 day HU and 28 day CON vs. 0 day CON animals, and nearly identical to that gain seen in the weight-bearing humerus. Mechanical properties at the proximal tibia exhibited a nonsignificant decline after HU vs. those of 0 day CON rats. At the femoral neck, a 10% decrement was noted in ultimate load in 28 day HU rats vs. 28 day CON animals. Middiaphyseal tibial bone increased slightly in density and area during HU; no differences in structural and material properties between 28 day HU and 28 day CON rats were noted. BFR at the tibial midshaft was significantly lower (by 90%) after 21 day HU vs. 0 day CON; this decline was maintained throughout 28 day HU. These results suggest there are compartment-specific differences in the mature adult skeletal response to hindlimb unloading, and that the major impact over 28 days of unloading is on cancellous bone sites. Given the sharp decline in BFR for midshaft cortical bone, it appears likely that deficits in BMD, area, or mechanical properties would develop with longer duration unloading.

Non-NASA Center↗

NASA NTRS2002

Skeletal unloading and dietary copper depletion are detrimental to bone quality of mature rats

This study was designed to examine the skeletal response to copper depletion and mechanical unloading in mature animals. In a 2 x 2 experimental design, 5.5-mo-old male Sprague-Dawley rats (n = 36) consumed either the control (AIN-93M) or Cu-depletion ((-)Cu) diet beginning 21 d before suspension and throughout the remainder of the study. Half of the rats in each dietary treatment group were either tail-suspended (TS) or kept ambulatory (AMB) for 28 d. Lower bone mineral densities (BMD) of 5th lumbar vertebra (L5) (P < 0.05) and femur were observed with (-)Cu and TS, but no differences were noted in the BMD of the humerus. Mechanical strength in the femur and vertebra decreased in response to TS, but were unaffected by copper depletion. Urinary deoxypyridinoline, an index of bone resorption, was significantly greater in TS rats, but unaltered by (-)Cu. No changes in serum or bone alkaline phosphatase activity, an indicator of bone formation, were observed. Our findings suggest that TS and (-)Cu decreased BMD in unloaded femur and vertebra but had no effect on normally loaded humerus. Bone loss with TS appeared to be related to accelerated bone resorption. Alterations in bone metabolism and bone mechanical properties in the mature skeleton resulting from (-)Cu warrant further investigation.

NASA Discipline Musculoskeletal↗

NASA NTRS1998

Growth dynamics and cytoskeleton organization during stem maturation and gravity-induced stem bending in Zea mays L

Characterization of gravitropic bending in the maize stem pulvinus, a tissue that functions specifically in gravity responses, demonstrates that the pulvinus is an ideal system for studying gravitropism. Gravistimulation during the second of three developmental phases of the pulvinus induces a gradient of cell elongation across the non-growing cells of the pulvinus, with the most elongation occurring on the lower side. This cell elongation is spatially and temporally separated from normal internodal cell elongation. The three characterized growth phases in the pulvinus correspond closely to a specialized developmental sequence in which structural features typical of cells not fully matured are retained while cell maturation occurs in surrounding internodal and nodal tissue. For example, the lignification of supporting tissue and rearrangement of transverse microtubules to oblique that occur in the internode when cell elongation ceases are delayed for up to 10 d in the adjacent cells of the pulvinus, and only occurs as a pulvinus loses its capacity to respond to gravistimulation. Gravistimulation does not modify this developmental sequence. Neither wall lignification nor rearrangement of transverse microtubules occurs in the rapidly elongating lower side or non-responsive upper side of the pulvinus until the pulvinus loses the capacity to bend further. Gravistimulation does, however, lead to the formation of putative pit fields within the expanding cells of the pulvinus.

Non-NASA Center↗

NASA NTRS1988

The effects of feedback lighting on the circadian rhythm of locomotor activity and the reproductive maturation of the male Djungarian hamster (Phodopus sungorus)

The non-parametric model of entrainment suggests that brief pulses of light, delivered between dusk and dawn can simulate the phasing effects of full photoperiods or even constant light (LL). Feedback lighting (LDFB) is a lighting condition where individual animals, otherwise in constant darkness (DD), are exposed to light in response to a monitored behavior. The specific purpose of this type of illumination is to expose the circadian cycle to light only during the subjective night. LDFB has been used to support this hypothesis in several species of nocturnal rodents and one species of diurnal primate by producing similar free-running periods in LDFB as in LL. This lighting condition has also been used to test the hypothesis that exposing the subjective night to even short duration light pulses will maintain reproductive function in long day breeders. In the Syrian hamster (Mesocricetus auratus), however, LDFB is not as photostimulatory as LL despite extensive light exposure during the subjective night. In the experiments presented here, a group of immature male Djungarian hamsters (Phodopus sungorus) were placed in individual light-tight sound attenuated chambers where they had free access to food, water and an activity wheel. The animals were exposed to one of four lighting conditions [DD, LL, LDFB or a neighbor control of feedback lighting (LDFB NC)] for approximately 30 days shortly after weaning. LDFB NC is a lighting condition where a neighbor control hamster receives the identical lighting regime as a paired animal exposing itself to LDFB, yet the neighbor has no control over it. A fifth group was exposed to a light-dark cycle of 16 hours of light and 8 hours of dark (LD16:8). This group was housed in cages in a colony room and did not have access to a running wheel. The free-running periods of the locomotor activity rhythms for hamsters exposed to LDFB and LL were not similar, unlike the results for rats, Syrian hamsters, mice, monkeys and even mature Djungarian hamsters. Immature hamsters exposed to DD and LDFB NC developed more slowly than animals exposed to LL or LD16:8, while hamsters in LDFB developed at an intermediate rate. Thus, it appears that LDFB, although capable of inducing reproductive function in immature Djungarian hamsters, is not as photostimulatory as may have been expected from current photoperiodic models, despite substantial light exposure during the subjective night. Furthermore, this data may suggest that the circadian system of 18-48 day old Djungarian hamsters are still undergoing organizational maturation.

NASA Program Space Biology↗

NASA NTRS1985

Mature phenotype in Hemerocallis plantlets fortuitously generated in vitro

Daylily plantlets generated on semi-solid media from morphogenetically competent cells or morphogenetically competent cells regenerated from protoplasts can give rise in aseptic culture to plantlets with a mature phenotype. The individual leaves of these plantlets open to the extreme base so that no encircling leaf sheath is present. This permits the overlapping bases and leaves to assume an open fan-like arrangement. The occurrence of fans correlates with exceptionally tightly sealed culture vessels and experiments to date suggest a gaseous component is associated with this change of growth form. It has not been possible to fix the mature growth mode, however, and new leaf growth assumes the more normal juvenile phenotype when the gaseous environment is altered by admitting or exposure to room air.

NASA Discipline Plant Biology↗

NASA NTRS2000

Correlation of lycopene measured by HPLC with the L, a, b color readings of a hydroponic tomato and the relationship of maturity with color and lycopene content

Tomatoes (Lycopersicon esculentum cv. Laura) were separated, according to the ripening stage, by a sensory panel into seven groups, and color was measured on the tomato surface with a Minolta Chroma meter. The L, a, b, hue, chroma, and lycopene content were plotted against the maturity stages of the tomatoes, and several good correlations were found. The a/b ratio and the lycopene content were the parameters that allowed six of seven maturity groups in the tomato to be statistically distinguished. The lycopene content, measured by HPLC, was also correlated with the color measurements, and the a, a/b, and (a/b)(2) color factors produced the best regressions. An estimation of the lycopene content in tomatoes can be achieved by using a portable chroma meter, with a possible field usage application. Equations to calculate the lycopene content of tomatoes based on the color readings are reported.

Non-NASA Center↗

NASA NTRS1996

Cortical bone growth and maturational changes in dwarf rats induced by recombinant human growth hormone

The growth hormone (GH)-deficient dwarf rat was used to investigate recombinant human (rh) GH-induced bone formation and to determine whether rhGH facilitates simultaneous increases in bone formation and bone maturation during rapid growth. Twenty dwarf rats, 37 days of age, were randomly assigned to dwarf plus rhGH (GH; n = 10) and dwarf plus vehicle (n = 10) groups. The GH group received 1.25 mg rhGH/kg body wt two times daily for 14 days. Biochemical, morphological, and X-ray diffraction measurements were performed on the femur middiaphysis. rhGH stimulated new bone growth in the GH group, as demonstrated by significant increases (P < 0.05) in longitudinal bone length (6%), middiaphyseal cross-sectional area (20%), and the amount of newly accreted bone collagen (28%) in the total pool of middiaphyseal bone collagen. Cortical bone density, mean hydroxyapatite crystal size, and the calcium and collagen contents (microgram/mm3) were significantly smaller in the GH group (P < 0.05). Our findings suggest that the processes regulating new collagen accretion, bone collagen maturation, and mean hydroxyapatite crystal size may be independently regulated during rapid growth.

NASA Discipline Musculoskeletal↗

NASA NTRS2004

Calcium balance in mature male rats with unloaded hindlimbs

BACKGROUND: Calcium balances, regulated by the calcium endocrine system, are negative during spaceflight but have not been reported in flight simulation models using fully mature small animals. METHODS: We conducted two calcium (Ca) balance studies in 6-mo-old male rats exposed to a model that unloads the hindlimbs (HU) for 4 wk. Control (C) and HU rats were fed diets with 0.5% Ca in the first and 0.1% Ca in the second study. Housing in metabolic cages enabled daily food and water intake measurements as well as collections of urine and fecal specimens. At necropsy, blood was obtained for measures of Ca-regulating hormones. RESULTS: Both C and HU rats adjusted to housing and diets with decreases in body weight and negative Ca balances during the first week of each experiment. Thereafter, averages of Ca balances were more negative in the unloaded rats than controls: -8.1 vs. -1.6 mg x d(-1) in rats fed 0.5% (p < 0.05). This difference was not due to urinary Ca excretion since it was lower in HU than C rats (1.27 +/- 0.51 mg x d(-1) vs. 2.35 +/- 0.82 mg x d(-1), p < 0.05). Fecal Ca in HU rats exceeded dietary Ca by 4-7%, Restricting dietary Ca to 0.1% was followed by an increase in serum 1,25-dihydroxyvitamin D (1,25-D) and greater intestinal Ca absorption than in rats fed 0.5% Ca. Ca balances in rats fed 0.1% Ca were also more negative in HU than C rats (-2.4 vs. -0.03 mg x d(-1), p < 0.05). Parathyroid hormone (PTH) was suppressed and 1,25-D increased in HU rats fed 0.5% Ca. C rats fed 0.1% Ca had increased PTH and 1,25-D was the same as in the HU group. CONCLUSION: After adaptation, Ca balances were more negative in mature male rats with unloaded hindlimbs than controls, an effect from increased secretion and loss of endogenous fecal Ca associated with increased 1,25-D in Ca-replete and Ca-restricted rats.

Hindlimb Suspension/physiology↗

NASA NTRS2008

Experimentation for the Maturation of Deep Space Cryogenic Refueling Technologies

This report describes the results of the "Experimentation for the Maturation of Deep Space Cryogenic Refueling Technology" study. This study identifies cryogenic fluid management technologies that require low-gravity flight experiments bring technology readiness levels to 5 to 6; examines many possible flight experiment options; and develops near-term low-cost flight experiment concepts to mature the core technologies. A total of 25 white papers were prepared by members of the project team in the course of this study. The full text of each white paper is included and 89 relevant references are cited. The team reviewed the white papers that provided information on new or active concepts of experiments to pursue and assessed them on the basis of technical need, cost, return on investment, and flight platform. Based on on this assessment the "Centaur Test Bed for Cryogenic Fluid Management" was rated the highest. "Computational Opportunities for Cryogenics for Cryogenic and Low-g Fluid Systems" was ranked second, based on its high scores in state of the art and return on investment, even though scores in cost and time were second to last. "Flight Development Test Objective Approach for In-space Propulsion Elements" was ranked third.

Chato, David J.↗

NASA NTRS2009

Test Plan for the Technology Maturation of Supersonic Inflatable Aerodynamic Decelerators

Supersonic inflatable aerodynamic decelerators (IADs) are drag devices intended to be deployed at high Mach numbers. In the application considered here they assist in the descent and landing of spacecraft on Mars. Although promising, present IAD technology is not yet sufficiently mature for use in the near future. This paper describes a technology maturation plan for tension cone IADs using subscale test articles to reduce development costs. As envisioned, the proposed test plan includes three phases: wind tunnel tests (subsonic), unpowered high-altitude flight tests (transonic), and powered high-altitude tests (supersonic). This test plan is based on a building block approach in which successful completion of each phase adds to the understanding of the behavior of IADs and reduces the risk of the subsequent, more expensive phases. By properly scaling the IADs, test articles of the same size and nearly the same construction can be used for all three phases. The final phase is a dynamically scaled flight test with IAD deployment at the same Mach number as the full-scale vehicle on Mars. Two full-scale example cases are presented: one for a single-stage system (15 m dia. IAD to subsonic retropropulsion), and another for a two-stage system (10.5 m dia. IAD to subsonic parachute). Using scale factors of 0.333 and 0.476 yield subscale test IADs of 5 m dia. The dynamically scaled powered flight test starts at Mach 4 and an altitude of 33.5 km. Existing balloons and rocket motors are shown to be adequate to meet the required test conditions.

Kelly, Jenny R.↗

NASA NTRS2011

Towards a Regolith Maturity Index for Howardites

The Dawn spacecraft has just arrived at asteroid 4 Vesta, parent of the howardite, eucrite and diogenite (HED) meteorites [1], to begin a yearlong surface study from orbit [2]. As Dawn will view a debris-covered surface, understanding the formation and mixing processes for the debris layer will strongly aid surface data interpretations. Howardites are polymict breccias mainly composed of clasts derived from basaltic (eucritic) and orthopy-roxenitic (diogenitic) parent materials [3]. Some howardites are poorly reworked (fragmental howardites) whilst others have been extensively gardened in an active regolith (regolithic howardites) [4]. The latter may represent an ancient, well-mixed regolith, whilst the former may be from more recent ejecta deposits [4]. Due to environmental differences, regolith development on Vesta differs in detail from that on the Moon [4-6]. We have been developing petrological criteria to apply to howardite thin sections to determine their relative regolithic maturity, which we are fine-tuning with comparison to noble gas data [7, 8]. Whilst we previously emphasized the abundance of reworked clasts (fragmental and impact-melt breccia clasts), this is an imperfect criterion: one howardite with abundant re-worked clasts (EET 99408) shows no evidence of solar wind Ne (SW-Ne), yet, two of our alleged fragmental howardites have clear SW-Ne signatures (LEW 85313, MET 00423) [7, 8]. We are now investigating the diversity in minor and trace element contents of low-Ca pyroxene clasts in howardites as a measure of regolith grade, and will begin analyses of such grains within reworked clasts. Our hypothesis is that regolithic howardites (and the breccia clasts they contain) will show greater diversity because they sampled more diverse diogenitic plutons than fragmental howardites, which formed from ejecta from only a few impacts [e.g. 4]. Our initial LA-ICP-MS work showed ranges in trace element diversity in low-Ca pyroxenes (estimated from the standard error of the mean of analyses), where those howardites considered of medium to high regolithic grade showed greater diversity [9]. Our EMPA results (from a larger howardite suite) show an overall greater diversity in our putative medium to high regolithic grade howardites, though there are exceptions. The greatest diversity is found for paired howardites GRO 95574 and GRO 95581, which were not considered regolithic in our initial study. We will continue investigating avenues to determine regolith maturity in thin section, factoring in bulk rock compositional data, and will coordinate these studies with noble gas results.

Mittlefehldt, David W.↗

NASA NTRS2011

Swingbed Amine Carbon Dioxide Removal Flight Experiment - Feasibility Study and Concept Development for Cost-Effective Exploration Technology Maturation on The International Space Station

The completion of International Space Station Assembly and transition to a full six person crew has created the opportunity to create and implement flight experiments that will drive down the ultimate risks and cost for human space exploration by maturing exploration technologies in realistic space environments that are impossible or incredibly costly to duplicate in terrestrial laboratories. An early opportunity for such a technology maturation experiment was recognized in the amine swingbed technology baselined for carbon dioxide and humidity control on the Orion spacecraft and Constellation Spacesuit System. An experiment concept using an existing high fidelity laboratory swing bed prototype has been evaluated in a feasibility and concept definition study leading to the conclusion that the envisioned flight experiment can be both feasible and of significant value for NASA s space exploration technology development efforts. Based on the results of that study NASA has proceeded with detailed design and implementation for the flight experiment. The study effort included the evaluation of technology risks, the extent to which ISS provided unique opportunities to understand them, and the implications of the resulting targeted risks for the experiment design and operational parameters. Based on those objectives and characteristics, ISS safety and integration requirements were examined, experiment concepts developed to address them and their feasibility assessed. This paper will describe the analysis effort and conclusions and present the resulting flight experiment concept. The flight experiment, implemented by NASA and launched in two packages in January and August 2011, integrates the swing bed with supporting elements including electrical power and controls, sensors, cooling, heating, fans, air- and water-conserving functionality, and mechanical packaging structure. It is now on board the ISS awaiting installation and activation.

Hodgson, Edward↗

NASA NTRS2013

Sustaining a Mature Risk Management Process: Ensuring the International Space Station for a Vibrant Future

The International Space Station (ISS) risk management methodology is an example of a mature and sustainable process. Risk management is a systematic approach used to proactively identify, analyze, plan, track, control, communicate, and document risks to help management make risk-informed decisions that increase the likelihood of achieving program objectives. The ISS has been operating in space for over 14 years and permanently crewed for over 12 years. It is the longest surviving habitable vehicle in low Earth orbit history. Without a mature and proven risk management plan, it would be increasingly difficult to achieve mission success throughout the life of the ISS Program. A successful risk management process must be able to adapt to a dynamic program. As ISS program-level decision processes have evolved, so too has the ISS risk management process continued to innovate, improve, and adapt. Constant adaptation of risk management tools and an ever-improving process is essential to the continued success of the ISS Program. Above all, sustained support from program management is vital to risk management continued effectiveness. Risk management is valued and stressed as an important process by the ISS Program.

Raftery, Michael↗