مترجم :آرش فراست

منبع : مجله S & T فوريه 2006

لازم به ذكر است اين نويسنده(  Sara Seager) اختر فيزيكدان عضو دانشگاه كارنيج (Carnegie) واشنگتن و متخصص مطالعه بر روي سيارات فراخورشيدي است

نوشته: چارلز وود

برگرفته ازمجله: 2006 Sky & Telescope  

برگردان از : آقاي منصور کاهه -عضو انجمن نجوم آماتوري ايران

پس از حدود 50 سال از شرع کاوشها در منظومه شمسی، اکنون به همه سیارات و بسیاری اجرام کوچکتر فضاپیما فرستاده ایم و با آنها بیشتر آشنا شده ایم، از تیر با سطح چروکیده اش تا نپتون با لکه تاریک بزرگش. اما سرزمین بزرگی در منظومه شمسی  به ندرت دیده شده و تقریباً فراموش شده است: سمت دیگر ماه.

نپتون آخرین و بیرونی ترین غول گازی است. قطر استوایی این سیاره 49500 کیلومتر است (760/30 مایل). اگر نپتون را توخالی فرض کنیم 60کره زمین در آن جای می گیرند. نپتون هر 165 سال یکبار مدارش به دور خورشید را طی می کند. نپتون 8 قمر دارد که تمامی آنها توسط وویجر کشف شده اند. یکروز نپتون 16 ساعت و 6 دقیقه و 42 ثانیه است نپتون در 23 سپتامبر سال 1846 توسط جوهان گاتفریدگال در رصدخانه برلین کشف شد.

مشخصات حلقه های نپتون

مشخصات قمرهای نپتون

منبع : سایت مجله علمی Elsevier  

سامانه سفر های فضايي که نام رسمي برنامه شاتل است و توسط ناسا به اين عنوان نام گذاري شده است.به طور رسمي در ژانويه ي ۱۹۷۲آغاز به کار کرد. اين سامانه سرنشين دار حمل و نقل فضايي با توانايي استفاده دوباره و توانايي پرتاب و قرارگرفتن در مدار را دارا است و مي تواند مانند يک هواپيما به زمين بازگردد و با اندکي تعميرات دوباره مورد بهره برداري قرار گيرد.شاتل جايگزين سامانه هاي پرتاب يک بار مصرفي شد که ناسا براي اهداف علمي در مدار زمين از آنها استفاده مي کرد.

 بقیه ....

When to plan your Star Party An evening with nice weather, few clouds and a Space Station sighting opportunity is best. Check for the best International Space Station sighting opportunities in your area and plan your party around that opportunity. Where to plan your Star Party A local museum or observatory, a park or an open field, or even your own backyard are good places to throw a party. Have a facility available to go inside, and enough activities to entertain the kids if the weather turns bad. You can always go back outside when the weather clears. You may also want to check weather related Web sites for forecasts of your area. Viewing the Stars Even though you want the highlight of your party to be the International Space Station passing overhead, you also want to allow plenty of time for stargazing. Rent or borrow a telescope and be sure to have a constellation map nearby. You could allow the following time for each activity for a 2 ½ hour party agenda 20 minutes Greet arrivals, socializing for adults, free play time for kids 20 minutes Refreshments 30 minutes Arts and crafts for kids 30 minutes Organized games, activities and space trivia 30 minutes Stargazing and watching the Space Station fly overhead 20 minutes Socializing for adults, free play time for kids Star Party Planning Schedule 4-6 weeks in advance Select date and time for party Choose location for party and make reservations, if necessary Develop party agenda (arts and crafts, refreshments, etc) Book entertainment, if any Don't forget to run the Skywatch applet and check the weather forecast 3-4 weeks in advance Purchase invitations Mail invitations (2 ½ weeks before party) Plan games and activities 2 weeks in advance Purchase party supplies (decorations, favors and activities) Be sure to buy extra in case additional people show up Plan menu and make grocery shopping list Arrange help to set up, clean, prepare & serve food & coordinate games Check sightings times again 1 week in advance Gather tables and chairs, toys, coolers, serving dishes, and other supplies you'll be using at the party Follow up with the invited guests who have not yet RSVP'd to determine final head count Order cake and balloons Prepare any foods that can be frozen for the following week 2-3 days in advance Charge video camera battery and make sure cameras are working Do grocery shopping (don't forget film) Get cash for paying helpers 1 day in advance Prepare remaining food, including cake or cupcakes Clean and child proof party area Party day Finish last minute food preparations Pick up cake and balloons (day before if Mylar balloons) Set up and decorate party area Set up games and prizes Star Party Supply Checklist Party Ware Tablecloths, plates, napkins, cups, utensils (forks, spoons, knives) Decorations Balloons (helium or regular), banners, signs, streamers, confetti Favors Favor bags, items to go in bag Food Cake, cupcakes, ice cream, candy, drinks (juice, soda), ice, snacks Misc. Serving dishes (trays, platters, baskets), serving utensils, camera, film, video camera, videotape, tables, chairs, ice chest Activities Games, arts and crafts

Image left: Space Shuttle Atlantis begins moving through the open door of the Vehicle Assembly Building for the rollout to Launch Pad 39A. First motion was at 8:19 a.m. EST. This will be the first launch from pad 39A in four years. Photo credit: NASA/Kim Shiflet + View High-res Image Image right: Perched atop the massive mobile launcher platform and crawler-transporter, Space Shuttle Atlantis rolls slowly toward Launch Pad 39A. The 3.4-mile trip along the crawlerway will take about 6 hours. Photo credit: NASA/Kim Shiflett + View High-res Image Image left: As Atlantis slowly makes its way to Launch Pad 39A, it passes the payload canister that delivered the payload to the pad. Photo credit: NASA/Kim Shiflett + View High-res Image Image right: The space shuttle inches its way up the ramp to the hardstand on Launch Pad 39A. At left is the fixed service and open rotating service structure. Between them is the water tower, containing 300 gallons of water used for sound suppression at liftoff. Photo credit: NASA/Kim Shiflett + View High-res Image Image left: Space Shuttle Atlantis arrives on the hardstand on Pad 39A after a 3.4 mile trek from the Vehicle Assembly Building. At left is the open rotating service structure that will be rolled to enclose the shuttle for protection. Photo credit: NASA/Kim Shiflett + View High-res Image Image right: Flags are flying at the entrance to Launch Pad 39A, where Space Shuttle Atlantis has come to a stop 'hard down' at 3:09 p.m. The shuttle spent about six hours rolling out to Pad 39A after leaving the Vehicle Assembly Building at 8:19 a.m. EST. Photo credit: NASA/Kim Shiflett + View High-res Image + STS-117 multimedia gallery Elaine M. Marconi NASA's John F. Kennedy Space Center

S0 Truss
Shuttle Mission: STS-110
ISS Assembly Mission: 8A

Dimensions: 13.4 meters x 4.6 meters (44 feet x 15 feet)
Weight: 13,971 kilograms (30,800 pounds)

The S0 Truss, the center segment of 11 integrated trusses, was attached to the top of the Destiny Laboratory on April 11, 2002. The S0 Truss acts as the junction from which external utilities are routed to the International Space Station's pressurized modules.

These utilities include power, data, video and ammonia for the Active Thermal Control System. The truss also provides a mounting point for electronic equipment such as the Main Bus Switching Units, four of the DC-to-DC Converter Units and four Secondary Power Distribution Assemblies. Also mounted on S0 are the station's four GPS antennas and two Rate Gyros.

Image to right: This interactive describes the individual parts that make up the Integrated Truss Structure.

The rear of the S0 Truss is occupied by a 6.4-meter (21-foot) radiator panel, which radiates heat transported from the truss' electronics boxes. The forward-facing rails of the S0 Truss and the other 10 truss assemblies form a track upon which the Mobile Transporter can move to different robotic arm worksites along the integrated truss structure.

S1 Truss
Shuttle Mission: STS-112
ISS Assembly Mission: 9A

Dimensions: 13.7 meters x 4.6 meters x 1.8 meters (45 feet x 15 feet x 6 feet)
Weight: 14,124 kilograms (31,137 pounds)

The S1 Truss, the first starboard truss segment, was attached to the starboard side of the S0 Truss Oct. 10, 2002. The S1 Truss provides structural support for the Active Thermal Control System, Mobile Transporter and one Crew and Equipment Translation Aid cart. The cart is manually operated by a spacewalker and can also be used as a work platform. The cooling system is like the one in a car radiator except that it uses 99.9 percent pure ammonia, compared to 1 percent in household products. The Thermal Radiator Rotary Joint rotates the three radiator structures in a 105-degree span either way to keep the three radiators panels in the shade; it also transfers power and ammonia to the radiators. The S1 Truss also has mounts for cameras and lights, as well as antenna support equipment for S-band communications equipment.

S3/S4 Truss
Shuttle Mission: STS-117
ISS Assembly Mission: 13A

The second starboard truss segment, the S3/S4 Truss, is attached to the first starboard truss segment, the S1.

S5 Truss
Shuttle Mission: STS-118
ISS Assembly Mission: 13A.1

The third starboard truss segment, the ITS S5 Truss, is attached to the S3/S4 Truss.

S6 Truss
Shuttle Mission: STS-119
ISS Assembly Mission: 15A

Fourth starboard truss segment, the S6 Truss, is delivered.

P1 Truss
Shuttle Mission: STS-113
ISS Assembly Mission: 11A

Dimensions: 13.7 meters x 4.6 meters x 1.8 meters (45 feet x 15 feet x 6 feet)
Weight: 14,003 kilograms (30,871 pounds)

The P1 Truss, the first port truss segment, was attached to the port side of the S0 truss Nov. 26, 2002. The P1 Truss provides structural support for the Active Thermal Control System, Mobile Transporter and one Crew and Equipment Translation Aid cart. The cart is manually operated by a spacewalker and can also be used as a work platform. The cooling system is like a car radiator except that it uses 99.9 percent pure ammonia, compared to 1 percent in household products. The Thermal Radiator Rotary Joint rotates the three radiator structures in a 105-degree span either way to keep the three radiators panels in the shade; it also transfers power and ammonia to the radiators. The P1 Truss also has mounts for cameras and lights, and antenna support equipment for both UHF and S-band communications equipment. The S-band equipment is currently on the P6 Truss.

P3/P4 Truss
Shuttle Mission: STS-115
ISS Assembly Mission: 12A

Delivers the second port truss segment, the P3/P4 Truss, to attach to the first port truss segment, the P1 Truss.

P5 Truss
Shuttle Mission: STS-116
ISS Assembly Mission: 12A.1

Delivers third port truss segment, the P5 Truss, to attach to second port truss segment, the P3/P4 Truss.

P6 Truss
Delivery Configuration:
Shuttle Mission: STS-97
ISS Assembly Mission: 4A

Temporarily installed on the Z1 truss during STS-97, the P6 integrated truss structure (ITS) will be relocated to its permanent location on the P5 truss during a later assembly mission. The four primary functions of the P6 are the conversion or generation, storage, regulation and distribution of electrical power for the space station. The station derives its power from the conversion of solar energy into electrical power. The P6 Photovoltaic Power Module performs this energy conversion.

Permanent Configuration:
Shuttle Mission: STS-120
ISS Assembly Mission: 10A

Delivers Node 2.

Z1 Truss
Shuttle Mission: STS-92
ISS Assembly Mission: 3A

ITS Z1 was an early exterior framework to allow first U.S. solar arrays on flight 4A to be temporarily installed on Unity for early power.

Are bigger bones stronger bones? Not necessarily, according to a recent NASA study that seeks to ensure healthy bones in astronauts.

A four-year study of the long-term effects of microgravity on the bones of International Space Station crew members showed that the astronauts, on average, lost roughly 11 percent of their total hip bone mass over the course of their mission.

Image at right: A Dual Energy X-ray Absorptiometry (DEXA) scan of a human hip bone, left, and a human spine, right. Credit: NASA

The study also found that a year after each crew member had returned to Earth, much of their lost bone mass was replaced. However, the bone structure and density had not returned to normal and signs of hip strength had not recovered at one year, although it had increased slightly compared to post-flight levels. Researchers say it could take much longer than a year to regain the lost strength.

The study's findings are important because bone loss during the course of a long transit to Mars and back could result in an increased risk of a bone fracture during activities on the Martian surface, or in the long term, back on Earth during the course of aging years after mission completion. Data from the study showed that, on average, crewmembers lost as much bone mass in one month on orbit as an elderly woman loses in an entire year.

Doctors treat millions of women and men for osteoporosis -- a disease in which the bones atrophy causing loss of density, becoming more porous and breaking more easily. Although healthy astronauts did not develop osteoporosis during their four- to six-month stays on the space station, the levels of bone loss documented were still enough to raise the concern for an increased risk for fracture when astronauts’ skeletons are subjected to applied loads with working, lifting or falling.

"The success of human exploration missions depends on finding countermeasures to overcome such effects on crew members," said Julie Robinson, International Space Station program scientist at NASA's Johnson Space Center in Houston. "There are important synergies between osteoporosis research on Earth, and studies of bone loss and recovery in healthy astronauts in space. Each area of study complements the other."

The research, formally named the Subregional Bone Assessment, was one of the first Human Research Program investigations to be completed onboard the space station. The program manages human health experiments to understand and reduce health and performance risks to astronauts in space.

Beginning with Expedition 2, from March to August 2001, and continuing through Expedition 8, from October 2003 to April 2004, 16 crew members participated in the study. The research focused on their weight bearing bones including the hip bones because studies had shown that the hip experiences the highest amount of bone loss during a space mission and the hip is the site of the most devastating osteoporotic fractures in the elderly.

The astronauts' bones were measured before and after their mission and one year after their return to Earth. The principal investigator for the experiment, Dr. Thomas Lang of the University of California in San Francisco, used X-ray Quantitative Computed Tomography to characterize the recovery of parts of the hip bone and changes in size and strength of the bones. The technique produces a series of cross-sectional images of the hip bone, allowing it to be quantified three-dimensionally without interference from overlying tissues. Lang used the X-ray technology to examine separately the bone's dense outer, or cortical, layer and its spongy inner, or trabecular, layer to determine bone loss in the hip and spine. The three-dimensional tomography measurements allowed researchers to determine whether loss is more prominent in one of those bone subregions.

"There's evidence from studies of aging that bone size increases as a compensation for loss of bone mass. We hypothesized that something similar would occur when crew members were re-introduced to gravity after long-duration spaceflight," said Lang. "Our one-year measurements were consistent with such an increase in bone size; however this increase in the bone may not have been enough to result in full recovery of the hip bone strength. We will continue to measure bone density to determine how much longer it takes to rebuild bone and bone strength, and whether these structural changes are permanent."
Contact:

Steve Roy
Marshall Space Flight Center