STP-02: DSX + попутчики - Falcon Heavy - Kennedy LC-39A - 25.06.2019, 06:30 UTC

[tnt22]

LightSail 2

https://ria.ru/20190801/1557074530.html

Космический парусник LightSail успешно поднял орбиту при помощи света
12:40


© Planetary Society

МОСКВА, 1 авг – РИА Новости. Микроспутник LightSail 2 успешно использовал свои паруса для того, чтобы поднять орбиту на два километра, что продемонстрировало работоспособность этой технологии. Об этом сообщает сайт Планетологического сообщества.

"Нас радует то, что миссия LightSail 2 завершилась полным успехом. Мы показали, что можем управлять положением зонда на орбите, используя лишь давление света Солнца. Это никому раньше не удалось продемонстрировать, и я очень горд тем, что наша команда справилась с этой задачей", — заявил Брюс Беттс (Bruce Betts), ведущий научный сотрудник Планетологического сообщества.

Микроспутник Lightsail-2 — уже третий прототип космического "парусника", идеологическим и технический наследник аппаратов Lightsail-1 и "Космос-1". Последний аппарат был первым зондом такого типа, который американские энтузиасты освоения космоса пытались запустить в 2005 году вместе с Российской академией наук и шведской компанией Cosmos Studios.

Запуск предшественника этого зонда, закончился не совсем удачно. Он был успешно выведен на орбиту в мае 2015 года, однако через два дня его компьютер пережил непонятный сбой, лишивший зонд связи с Землей на протяжении последующей недели. После того, как аппарат раскрыл солнечные батареи, он еще раз перестал откликаться на сигналы из ЦУП, что создатели зонда связали с наличием проблем в работе аккумуляторов Lightsail-1.

Позже связь была еще раз восстановлена и аппарат смог развернуть паруса. После этой процедуры он снизил орбиту, вошел в атмосферу и сгорел. Руководство Планетологического сообщества признало этот запуск успешным и начало готовиться к отправке второго зонда на орбиту.

Первый зонд, как отмечают его создатели, не мог использовать свои паруса для набора скорости, так как он находился на слишком небольшой высоте, где этому мешало притяжение Земли, ее атмосфера и масса других факторов.

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По этой причине его "наследник" был запущен на высоту в 700 километров от поверхности планеты, где его пятиметровый квадратный парус может выработать достаточно тяги для того, чтобы не только удерживать себя от падения на Землю, но и "сбежать" от ее гравитации.

Помимо новых батарей и компьютера, защищенного от сбоев, LightSail-2 включал в себя два новых прибора. В их число вошли уголковый отражатель, позволявший ученым точно замерять высоту орбиты "солнечного парусника" с Земли, а также набор маховиков и гироскопов, необходимых для того, чтобы зонд мог постоянно "смотреть" на Солнце.

Новая версия аппарата была выведена на орбиту месяц назад на борту ракеты Falcon Heavy, после чего она успешно раскрыла солнечные батареи, получила первые фотографии и приступила к раскрытию парусов. Это произошло неделю назад. После этого пилоты миссии успешно использовали свет Солнца для того, чтобы поднять высоту орбиты LightSail-2 на два километра.

"Мы ожидали этого момента несколько десятилетий. Карл Саган говорил о возможности подобных полетов еще в 1977 году, когда я был его учеником, однако сама идея была озвучена еще в начале XVII века Иоганном Кеплером, заметившим, что свет Солнца порождает хвосты комет. Lightsail-2 перевернет мир космических полетов и изучения космоса", — добавил Билл Най (Bill Nye), известный популяризатор науки и исполнительный директор общества.

По текущим планам руководителей миссии, Lightsail-2 будет повышать орбиту на протяжении еще примерно месяца до тех пор, пока ее нижняя точка – перигей – не подойдет опасно близко к Земле. После этого аппарат начнет терять высоту и сгорит в атмосфере примерно через год, проложив дорогу для полетов более серьезных "космических парусников".

[Старый]

tnt22 написал:
По текущим планам руководителей миссии, Lightsail-2 будет повышать орбиту на протяжении еще примерно месяца до тех пор, пока ее нижняя точка – перигей – не подойдет опасно близко к Земле.

Чтото я не совсем понял что означает "повышать"...  :oops: 

[Чебурашка]

Предполагаю, что эффект от действия солнечного паруса на замкнутой орбите - период не меняется, растёт эксцентриситет.
т.е. апогей растёт, перигей падает - пока не завалится в атмосферу.

[Старый]

Чебурашка написал:
Предполагаю, что эффект от действия солнечного паруса на замкнутой орбите - период не меняется, растёт эксцентриситет.
т.е. апогей растёт, перигей падает - пока не завалится в атмосферу.

Предполагаю что да. Но почему это называют "подъёмом орбиты"?  :oops: 

[tnt22]

На текущий момент определены (в т.ч. с перенумерацией) 20 объектов запуска

[tnt22]

 Jonathan McDowell‏ Подлинная учетная запись @planet4589 5 мин. назад
LightSail-2 orbital eccentricity continues to increase following sail deployment

[tnt22]

 Jonathan McDowell‏ Подлинная учетная запись @planet4589 5 мин. назад
Upate on Lightsail-2 orbit evolution. Looks like the eccentricity increase may be slowing

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tnt22 написал:
 

Jonathan McDowell‏  Подлинная учетная запись @planet4589    5 мин. назад
 LightSail-2 orbital eccentricity continues to increase following sail deployment  

С 1 июля 2019 период LightSail-2 уменьшился на 0.6 секунды. Соответственно, средняя высота немного возросла.

[Liss]

cross-track написал:
 

tnt22 написал:
 

Jonathan McDowell‏  Подлинная учетная запись @planet4589     5 мин. назад  
 LightSail-2 orbital eccentricity continues to increase following sail deployment  

С 1 июля 2019 период LightSail-2 уменьшился на 0.6 секунды. Соответственно, средняя высота немного возросла.

В смысле -- уменьшилась на 0.5 км в период с 23 июля (развертывание паруса) по сей день, будучи до того постоянной.
Как, впрочем, дедушка МакДауэлл написал по горячим следам радостного крика разработчиков.

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Liss написал:
 

cross-track написал:
 

С 1 июля 2019 период LightSail-2 уменьшился на 0.6 секунды. Соответственно, средняя высота немного возросла.

В смысле -- уменьшилась на 0.5 км в период с 23 июля (развертывание паруса) по сей день, будучи до того постоянной.
Как, впрочем, дедушка МакДауэлл написал по горячим следам радостного крика разработчиков.

Вы меня правильно поправили - в смысле уменьшилась высота, а не возросла. Парус может как поднимать, так и опускать высоту, и опускание высоты тоже может иметь смысл, если разработчики того хотели. Но что-то я в этом сомневаюсь...

[tnt22]

Jonathan McDowell‏Подлинная учетная запись @planet4589 9 мин. назад
The LightSail-2 solar sail continues to increase its orbital eccentricity while losing overall orbit height

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 Jonathan McDowell‏ Подлинная учетная запись @planet4589 50 мин. назад

Reviewing the status of the satellites from the Space Test Program STP-2/Falcon Heavy launch in June:


48 мин. назад

The @michigantech Oculus-ASR satellite ejected a calibration sphere on about Jul 1. The sphere's orbit has been rapidly decaying but has not been tracked since Aug 7. It may have reentered but no decay notice has been issued.


46 мин. назад

The @USNRL TEPCE space tether experiment is one of six objects from the launch that remain unidentified. I presume it to have failed, and probably the 1 km space tether did not deploy.


44 мин. назад

The E-TBEX A and B ionospheric research satellites from @UMich/SRII were reported to be having problems on the day after launch and with no further reports it seems probable that they have both failed.


42 мин. назад

The StangSat satellite from Merritt Island High School also remains unidentified. It was only meant to return data during the launch phase so may have worked, although that points out an issue with satellite registration for short lived payloads in cluster launches


37 мин. назад

The six Taiwan/NOAA COSMIC-2 satellites have been adjusting their orbits by a km or so. However COSMIC 2-1 dropped off tracking on Jul 22. A single element set on Aug 13 shows it 150 km lower and may be spurious; there's nothing since.


35 мин. назад

Now maybe COSMIC2-1 had a problem and its orbit was lowered, but then I'd expect regular TLE data showing it in the lower orbit for the last couple of weeks, or a decay notice. So something funny here on 44349, @18SPCS !


29 мин. назад

The orbit for 44342 GPIM seems to change in a very similar way to the COSMIC2 sats.  (I wonder if GPIM and COSMIC2-1 could have gotten cross-tagged?)

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 Jonathan McDowell‏ Подлинная учетная запись @planet4589 58 мин. назад

A small calibration sphere ejected from the Oculus-ASR satellite on about Jul 1 reentered on Aug 10, Space-Track reports belatedly. A second sphere known to be aboard Oculus-ASR has not been catlaoged - maybe it hasn't been ejected yet

[tnt22]

Идентифицирован 21-й объект запуска - FALCONSAT-7

 

[tnt22]

НОРАД идентифицировал 22-й объект запуска - TEPCE (44346 / 2019-036H)
 

[Alex-DX]

Было?
 классное кино https://twitter.com/SpaceX/status/1191779329467748353

[tnt22]

https://www.planetary.org/blogs/jason-davis/heres-what-we-learned-so-far-ls2.html

Jason Davis • January 10, 2020

Here's What We've Learned So Far fr om LightSail 2

High above Earth, The Planetary Society's LightSail 2 spacecraft is still sailing on sunbeams. During the 5 months since LightSail 2 deployed its solar sail on 23 July 2019, the spacecraft has continued to demonstrate the first controlled solar-sailing flight in Earth orbit.

The LightSail 2 team is releasing a paper today that describes new results from the mission. Purdue University's Justin Mansell is also presenting the results at the 30th Space Flight Mechanics Meeting in Orlando, Florida. The paper recaps mission events through late November, discusses the performance of the solar sail and attitude control system, and describes how the spacecraft's orbit has changed.


The Planetary Society
LIGHTSAIL 2 NEAR THE MIDDLE EAST
LightSail 2 captured this image of the Gulf of Oman and the Persian Gulf on 14 December 2019. The sail appears slightly curved due to the spacecraft's 185-degree fisheye camera lens. The image has been color corrected and some of the distortion has been removed.

Earth's atmosphere is a drag

LightSail 2 flies at a higher altitude than most satellites in low-Earth orbit. While the International Space Station orbits Earth at an altitude of about 400 kilometers, LightSail 2 orbits at about 720 kilometers. Since fewer spacecraft orbit at LightSail 2's altitude, there wasn't enough data on Earth's atmospheric density to reliably predict how much atmospheric drag would slow down the spacecraft. We now know for certain that the atmosphere at 720 kilometers is dense enough to overcome the thrust imparted by solar sailing.

The team uses a simple on-off sail control strategy each orbit, turning the sail edge-on to the Sun's rays when the spacecraft is traveling toward the Sun, and face-on to the Sun when moving away from it. Out of each 100-minute orbit, LightSail 2 spends 67 minutes either in eclipse or moving toward the Sun. Of the remaining 33 "sail-able" minutes each orbit, the spacecraft spends about 5 minutes turning to the desired orientation. Therefore, LightSail 2 enjoys at most 28 minutes of each orbit in an orientation for capturing the momentum of solar photons to change its velocity.


Mansell and his colleagues documented LightSail 2's orbital change during time intervals in which it was actively orienting itself for solar sailing and compared that change to periods in which the orientation was not controlled. When the spacecraft was randomly oriented, its semimajor axis—a measure of the size of the orbit—shrank by an average of 34.5 meters per day. When it was solar sailing, the orbit only shrank by an average of 19.9 meters per day. Yet, the rate is highly variable and the semimajor axis actually increased by as many as 7.5 meters some days when sailing, which means LightSail 2 increased its orbital energy during those periods.

https://www.youtube.com/embed/F6RjDvk-cNE
LIGHTSAIL 2 SAMPLE ORBIT ANIMATION
This video shows LightSail 2's orientation with respect to the Sun during a single orbit on 24 September 2019. Gaps between data points have been interpolated. The red line shows the direction of the Sun, and the blue line shows the direction of the local magnetic field. When the sailing command is "feather," LightSail 2 attempts to turn its sail edge-on to the solar photons, meaning the red arrow should be roughly parallel with the sail. (The Sun to -z angle should be roughly 90 degrees.) When the sailing command is "thrust," LightSail 2 tries to turn its sail broadside to the solar photons, meaning the red arrow should roughly make a 90-degree angle with the sail. (The Sun to -z angle should be roughly 0 degrees.) For more, see https://www.planetary.org/blogs/jason-davis/heres-what-we-learned-so-far-ls2.html. Video credit: Justin Mansell, Purdue University

The increases in orbital energy from solar sailing are generally not enough to overcome atmospheric drag, so LightSail 2's orbit is gradually decaying.  Pre-launch orbital models predicted that the spacecraft would reenter Earth's atmosphere and burn up about a year after sail deployment. But since there are few prior examples of spacecraft like LightSail 2 having high area-to-mass ratio, the actual timeline will provide new information about orbital decay rates.

Future solar sails will be used in higher Earth orbits, or on interplanetary trajectories. NASA's NEA Scout will ride a Space Launch System rocket out near the Moon and then use solar sailing to visit an asteroid. The LightSail 2 team is sharing data and expertise with the NEA Scout team.

The ups and downs of LightSail 2's orbit

If you've looked at our mission control page over the past few months, you may have noticed LightSail 2's orbital high and low points above the Earth, known as the apogee and perigee, respectively, have been cycling up and down.


This chart shows LightSail 2's orbit apogee and perigee as reported by space-track.org since 8 July 2019. Sail deployment occurred on 23 July 2019. The entire dataset can be downloaded here.

Right after sail deployment in July, LightSail 2's apogee increased, while perigee decreased. In September, the trend reversed: apogee decreased, while perigee increased. In late October, the trend reversed again. And then it began reversing again in December.

This cycle has two causes: Earth's nonspherical shape, and its orbital motion around the Sun. Earth's diameter at the equator is about 42 kilometers larger than it is at the poles, making its gravity stronger over the equator. This uneven gravity makes the positions of perigee and apogee precess, or wobble; if you were watching the spacecraft's orbit from high above the north pole, you'd see it wobbling like a hula hoop spinning around your waist. While all this is happening, Earth is also revolving around the Sun, changing the angle between the light pressure from the Sun and the positions of LightSail 2's apogee and perigee.


Justin Mansell, Purdue University
LIGHTSAIL 2 ORBITAL WOBBLE
Earth's uneven gravity makes LightSail 2's orbit precess, or wobble. The direction of the Sun (red arrow) relative to the orbit also changes over time as the Earth orbits the Sun.

The best orientation for raising LightSail 2's apogee is when perigee occurs on the thrust-on side of the orbit, as shown above in blue. Conversely, when perigee occurs on the thrust-off side of the orbit, as shown above in red, apogee decreases.

Momentum management

One of the mission's major challenges stems from LightSail 2's single momentum wheel, which the spacecraft uses to swing itself parallel and perpendicular to the Sun's rays each orbit. The wheel hits a pre-defined speed lim it about once per day, whereupon LightSail 2 must exit solar-sailing mode and stabilize itself with its electromagnetic torque rods.

Early in the mission, the team was doing this manually, which proved to be inefficient, especially when communications were spotty, or when the spacecraft was suffering from other technical glitches. The process is now automated, which has improved performance. In the new paper, the team conveys an important lesson for other solar sail spacecraft in Earth orbit: managing the momentum imparted by frequent sail orientation changes is a key technical challenge.

Power generation

LightSail 2 only has solar cells on one side of its solar sail. LightSail 1 had a solar panel on the opposite side, but this was removed for LightSail 2's design so engineers could install a cluster of special mirrors used to laser-range the spacecraft from Earth. This process involves zapping LightSail 2 with a laser and measuring the reflection time to more accurately determine the spacecraft's orbit.

Jason Davis / The Planetary Society
LIGHTSAIL 2 WITH MINI-DVD
LightSail 2 flew into space with a mini-DVD containing a Planetary Society member roster, a list of Kickstarter contributors, and names and images from the Society's "Selfies to Space" campaign.

In certain orientations, LightSail 2's solar sail entirely shadows the solar panels, and the spacecraft does not receive adequate power from the Sun, causing brownouts. The team has been able to work around brownouts by carefully managing the spacecraft's power budget and attitude-control mode. Future solar sail spacecraft should take sail shadowing into account for mission planning.

What's next? 

The LightSail 2 team recently added a new control mode to the spacecraft called sun-pointing. This mode is designed to keep the solar sail face-on to the Sun throughout its full orbit. A constantly Sun-facing attitude won't reduce orbital decay like the on/off mode does, but it reduces momentum-wheel saturation and provides a favorable orientation for battery charging. It will also test the spacecraft's pointing accuracy, and could provide a more consistent initial attitude for starting for on-off thrust maneuvers.

The mission team will also continue to take pictures. The technical reason for pictures is to document the sail's condition and shape, but the pictures are also beautiful to look at for the team and public alike. You can see all raw images from the spacecraft here, or view processed images in our LightSail 2 multimedia gallery.

Finally, as the orbit shrinks, the team will study the effect of the sail on the rate of orbital decay, sharing the data with other teams who are studying the use of drag sails to deorbit spacecraft.


The Planetary Society
MADAGASCAR FROM LIGHTSAIL 2
LightSail 2 captured this image on 24 November 2019. The southern tip of Madagascar appears at right. North is approximately at the bottom of the image. A faint smoke plume can be seen casting a shadow. The sail appears slightly curved due to the spacecraft's 185-degree fisheye camera lens. The image has been color corrected and some of the distortion has been removed.


The Planetary Society
AUSTRALIA AND NEW GUINEA FROM LIGHTSAIL 2
LightSail 2 captured this image on 25 November 2019. The top end of Australia's Northern Territory is in the center of the image. North is approximately at the bottom of the image. The city of Darwin is beneath the clouds near the tip of the sail's middle boom. The island of New Guinea can be seen to the left. A lens flare also appears in the left part of the image. The sail appears curved due to the spacecraft's 185-degree fisheye camera lens. The image has been color corrected and some of the distortion has been removed.

[tnt22]

https://spacenews.com/tethers-unlimited-says-early-results-of-deorbit-hardware-test-promising/

Tethers Unlimited says early results of deorbit hardware test promising
by Caleb Henry — January 23, 2020

WASHINGTON — The first of four small satellites currently flying with Tethers Unlimited's  experimental deorbit module on board began its slow descent last fall and is coming down according to plan, spacecraft hardware company Tethers Unlimited said Jan. 21.


Observations from the U.S. military's Space Surveillance Network show the Prox-1 satellite deorbiting more than 24 times faster than before deploying the tape. Credit: Tethers Unlimited.

Prox-1, a 71-kilogram cubesat that launched into a low Earth orbit in June on a SpaceX Falcon Heavy rocket, successfully deployed a 70-meter length of conductive tape in September that is creating enough drag to deorbit the satellite much sooner than simply abandoning the satellite.

"[ I]nstead of remaining in orbit for hundreds or thousands of years, the Prox-1 satellite will fall out of orbit and burn up in the upper atmosphere in under ten years," Tethers Unlimited CEO Rob Hoyt said in a news release.

Hoyt said observations from the U.S. military's Space Surveillance Network showed the Prox-1 satellite deorbiting more than 24 times faster than before deploying the tape.

Prox-1, built by the Georgia Institute of Technology with funding from the U.S. Air Force Research Laboratory's University Nanosatellite Program, is in a 717-kilometer low Earth orbit, Hoyt told SpaceNews by email. Prox-1, which Georgia Tech owns and operates, is one of 24 small satellites that launched on Falcon Heavy last year as part of the U.S. Defense Department's Space Test Program-2 mission.

Hoyt said another satellite from the Falcon Heavy launch, NPSat-1, also has a Terminator Tape module onboard that is set to deploy toward the end of 2020.

Tethers Unlimited also has Terminator Tape on two Aerospace Corp. cubesats currently in orbit, he said, and is waiting for their operator's mission to conclude before releasing the tapes.

Terminator Tape works by interacting with the space environment to create drag, accelerating the time it takes for the satellite to fall out of orbit and reenter the atmosphere.

"For a typical nanosat/microsat, the Nanosat Terminator Tape should meet the 25-year [de-orbit] requirement up to about 850 kilometers," Hoyt said. He estimated Terminator Tape can work for cubesats in orbits as high as 1,100-kilometers.

Hoyt said Terminator Tape can be made longer and wider for larger satellites.

Hoyt said Tethers Unlimited could potentially attach Terminator Tape modules to defunct satellites using the LEO Knight servicer it is developing. That servicer, which is specifically focused on low Earth orbit, is still three to four years from completion, Hoyt said.

LEO Knight should be capable of attaching Terminator Tape to abandoned spacecraft such as Iridium's defunct satellites, Hoyt said, but Tethers Unlimited would need to be paid more than $10,000 per satellite — the price Iridium CEO Matt Desch floated in December as a conversation starter.

Hoyt said the price for deorbiting satellites using LEO Knight and Terminator Tape would need to be "somewhere between one to two orders of magnitude higher" to make the business case close.

Iridium has 30 dead first-generation satellites still in orbit, many of them near the altitude of the Prox-1 satellite.

Hoyt said Terminator Tape and its timer cost the company about $500,000 to develop using a combination of internal funding and U.S. government research grants. The modules weigh less than a kilogram, according to the company.

Tethers Unlimited has another Terminator Tape demonstration mission launching on a Rocket Lab Electron later this year, Hoyt said. That mission, called DragRacer, consists of two identical satellites in identical orbits. Only one of the DragRacer satellites will unfurl Terminator Tape, allowing Tethers Unlimited to measure exactly how much faster the deorbit system causes a spacecraft to reenter.

Boeing subsidiary Millennium Space Systems is building the DragRacer spacecraft. TriSept Corp. arranged the launch. Millennium Space Systems is funding the DragRacer mission, with Tethers Unlimited contributing, Boeing spokeswoman Cheryl Sampson told SpaceNews Jan. 23. Hoyt declined to specify how much funding Tethers Unlimited is providing for the mission.

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[tnt22]

Jonathan McDowell✔@planet4589 7:56 AM - Feb 5, 2020

The TEPCE cubesat reentered on Feb 1.  It was launched last June and was meant to deploy a 1 km tether. A large change in its decay rate on Nov 17 suggests the tether was indeed deployed on that date, leading to its rapid reentry.  (TEPCE in red on the plot)

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 Jonathan McDowell‏ @planet4589 11 ч. назад

Altitude of Lightsail-2 versus time  (red: apogee, perigee;  blue; average of the two).; shows that drag is a much bigger effect that any net sail thrust.  #YurisNight