[Project Topics] AKATSUKI onboard instruments to move to regular operation

The Venus Climate Orbiter “AKATSUKI” (PLANET-C) conducted a trial jet thrust of its onboard orbit maneuver engine (OME) twice on September 7 and 14, but acceleration by the thrust was only about one ninth of expectations, and the generated thrust was also only about 40 Newton. With these results, we found that we cannot gain enough specific impulse for orbit maneuvering by the OME. Also, we suspect that the OME may have gradually been damaged; therefore, we decided not to use the OME. We will carry out the orbit maneuver using the reactoion control system (RCS) thruster to meet Venus in 2015. We plan to conduct a peri-Venus orbit maneuver in early November.

Drawing: Relative locations between Akatsuki, Venus and Earth at orbit maneuver (Sun orbit/Current orbit)

The Venus Climate Orbiter “AKATSUKI” (PLANET-C) conducted a trial jet thrust of its onboard orbit maneuver engine (OME) twice on September 7 and 14, but acceleration by the thrust was only about one ninth of expectations, and the generated thrust was also only about 40 Newton.
With these results, we found that we cannot gain enough specific impulse for orbit maneuvering by the OME. Also, we suspect that the OME may have gradually been damaged; therefore, we decided not to use the OME. We will carry out the orbit maneuver using the reactoion control system (RCS) thruster to meet Venus in 2015. We plan to conduct a peri-Venus orbit maneuver in early November.
Drawing: Relative locations between Akatsuki, Venus and Earth at orbit maneuver/ Sun orbit (current orbit)

JAXA conducted the second jet thrust test(*1) from the orbit maneuver engine (OME) aboard the Venus Climate Orbiter “AKATSUKI” (PLANET-C) on Sept. 14 (Japan Standard Time.) Through analysis of acquired test data, we found that acceleration by the jet thrust was less than the expected value similarly to the first test result.
Based on those test results, we would like to study the measures to be taken.
The satellite is in condition after the second test.
*1: The second test aimed at reconfirming the status of the jet thrust from the OME. The test duration was about five seconds as planned.

JAXA performed the second jet thrust(*1) test from the orbit maneuver engine (OME) aboard the Venus Climate Orbiter “AKATSUKI” (PLANET-C) at the scheduled time of 11:50 a.m. on Sept. 14 (Japan Standard Time) as part of studying an orbit change plan for the AKATSUKI to meet with Venus. We have confirmed the jet thrust from the OME.
We will analyze acquired telemetry data, and study the orbit change plan of the AKATSUKI.
*1: The second test aimed at reconfirming the status of the jet thrust from the OME. The planned test duration was about five seconds.

JAXA performed the first test jet thrust(*1) from the orbit maneuver engine (OME) aboard the Venus Climate Orbiter “AKATSUKI” (PLANET-C) on Sept. 7 as part of studying an orbit change plan for the AKATSUKI to meet with Venus. Through this test, we found that acceleration by the jet thrust was less than the expected value; therefore, we decided to shorten the time duration of the second test(*2) slated for Sept. 14 to about 5 seconds because the originally expected acceleration value was the baseline for the second test. We will jet the thrust for about five seconds again to reconfirm the thrusting condition of the OME.
The satellite is in good condition after the first test jet thrust.
*1: Test thrust aimed at quantitatively understanding postural disturbance (including horizontal thrust.) The thrust duration was two seconds as planned.
*2: The second test originally aimed to verify the attitude control logic. The planned thrust duration was 20 seconds.

JAXA carried out the first test jet thrust(*1) from the orbit maneuver engine (OME) aboard the Venus Climate Orbiter “AKATSUKI” (PLANET-C) as part of studying an orbit change plan for the AKATSUKI to visit Venus.We have confirmed that the OME jetted out thrust at 11:50 a.m. on September 7 (Japan Standard Time.)
We will analyze the acquired telemetry data and prepare for the second test jet thrust(*2) scheduled for Sept. 14 (JST.)

*1: Test thrust aimed at quantitatively understanding postural disturbance (including horizontal thrust.) The planned thrust duration was two seconds.
*2: The second test aims to verify the attitude control logic. The planned thrust duration is 20 seconds.

JAXA made the following report at the AKATSUKI’s third investigation meeting for the Space Activities Commission on June 30.
As a result of analysis and verifications of the AKATSUKI’s anomaly cause estimated at the first and second investigation meetings, the highest possibility was found to be damage to the thruster nozzle of the orbit maneuver engine due to closure of the check valve during the orbit injection maneuver.
We will determine if we can reignite the damaged thruster nozzle through a ground test as well as an emission test of the onboard engine. Based on the results of these tests, we will prepare for an orbit injection maneuver to Venus hoping for the AKATSUKI to meet with Venus in November 2015.
Photo: A firing test for Venus orbit injection

JAXA is currently investigating the failure cause of the Venus orbit injection of the Venus Climate Orbiter “AKATSUKI.” During the course of the orbiter functional verification after data acquisition at the periVenus, we were able to obtain some Venus images captured by the AKATSUKI at around 9:00 a.m. on Dec. 9 (Japan Standard Time.)
(Images: from left, an image shot by the UVI, IR1, and LIR. The images are artificially colored: The UVI image with blue, and the IR1 image with orange.)

JAXA found that we have failed to inject the Venus Climate Orbiter “AKATSUKI” into the planned Venus orbit after conducting the Venus orbit insertion maneuver (VOI-1) on December 7. While we set up a new investigation team to study the cause and countermeasures, we will also review the Venus orbit injection plan again to take the next opportunity in six years when the AKATSUKI flies closest to Venus.

JAXA conducted the Venus orbit insertion maneuver (VOI-1) for the Venus Climate Orbiter “AKATSUKI” at 8:49 a.m. on December 7 (Japan Standard Time,) but, unfortunately, we have found that the orbiter was not injected into the planned orbit as a result of orbit estimation. The “AKATSUKI” was launched from the Tanegashima Space Center on May 21.
JAXA has set up an investigation team to study the cause of the failure.
We will update you with the investigation results and AKATSUKI operation status on the web.

JAXA decided to emit jets from the orbital maneuvering engine (OME) of the AKATSUKI at 8:49:00 a.m. on Dec. 7 (Japan Standard Time, all the following dates and time are in JST) to inject the orbiter into the Venus orbit. Under the current schedule, the OME jet emission will be completed at 9:01:00 a.m. on the same day, and the Venus orbit will be determined around 9:00 p.m. also on the same day after some attitude control maneuvers including the Earth pointing maneuver of the Z axis.
The AKATSUKI will study the Venus atmosphere for about two years after being injected into the Venus orbit.

On October 8, the onboard cameras of the AKATSUKI took images of a part of Sagittarius. For this image shooting, we made the AKATSUKI face its cameras’ installed side to Sagittarius while the explorer was communicating with the Usuda Deep Space Center, and took images by activating the Longwave IR camera (IRC,) Ultraviolet Image (UVI,) 1µ m camera (IR1,) and 2µ m camera (IR2.)
The AKATSUKI onboard cameras can capture invisible light such as ultraviolet or infrared rays. Thus Sagittarius shot by the UVI, which observes ultraviolet rays, and the IR1, which catches infrared rays, looks different from what the human eye can see.
Concerning the LIR and IR2, it was predicted in advance that they could not detect a star under the observed wave-length region and temperature conditions of the observation this time. We, therefore, confirmed that each camera works properly according to their respective functional conditions.

On June 28 (Japan Standard Time,) the Venus Climate Orbiter “AKATSUKI” successfully jetted the thrust of 500 Newton by its orbital maneuvering engine (OME) at a distance of 14.6 million km from the Earth or 1.06 Astronomical Units (AU) from the sun. The OME was a newly developed ceramic thruster made of silicon nitride (Si3N4.) It is the first time in the world to successfully generate the thrust by the ceramic thruster in space.
This engine is mainly used for retrofiring when the orbiter enters the Venus orbit, and the verification this time enabled us to confirm that the orbit control was carried out as scheduled.
The next orbit control is scheduled to be in early November, and the orbiter will be at the closest point to Venus and injected into the Venus orbit on December 7 (JST.)

On May 21, JAXA confirmed that the Venus Climate Orbiter “AKATSUKI,”
launched by the H-IIA F17, successfully performed a sequence of scheduled operations such as the deployment of the solar array paddles and sun acquisition.

We have also received earth images taken by the AKATSUKI while verifying the condition of onboard devices at about 250,000 km above the Earth at around 8:50 p.m. on May 21.

The H-IIA Launch Vehicle No. 17 (H-IIA F17) with the Venus Climate Orbiter “AKATSUKI” onboard was launched at 6:58:22 a.m. on May 21 (Japan Standard Time) from the Tanegashima Space Center. The H-IIA F17 flew smoothly, and, at 27 minutes and 29 seconds after liftoff, the AKATSUKI was separated from the H-IIA.
We will update you with the latest information on the AKATSUKI on the special site.
(Photo: Mitsubishi Heavy Industries)

The launch of the Venus Climate Orbiter “AKATSUKI” and the Small Solar Power Demonstrator “IKAROS” by the H-IIA Launch Vehicle No. 17 was rescheduled at 6:58:22 a.m. on May 21 (Fri. Japan Standard Time, JST) after carefully studying the weather conditions.

Accordingly, the live launch report will begin at 6:30 a.m. on May 21(Fri., JST.) The report will be broadcast not only through the Internet, but also at JAXA i, Sagamihara Campus and other public viewing locations including some universities. You can also watch it through some CATV and cell phone providers.

On May 9, the encapsulated Venus Climate Orbiter “AKATSUKI” and the Small Solar Power Sail Demonstrator “IKAROS” were transported to the Vehicle Assembly Building (VAB), where the H-IIA Launch Vehicle No. 17 was waiting for their payloads. They will be loaded onto the launch vehicle, and the final inspection will be carried out to be ready for the launch on the 18th.

On May 4, the Venus Climate Orbiter “AKATSUKI” and the Small Solar Power Sail Demonstrator “IKAROS” were encapsulated in the fairing at the Spacecraft and Fairing Assembly Building (SFA) at the Tanegashima Space Center (TNSC.) The fairing covers the payloads to protect them from air resistance, friction heat, and acoustic vibrations during launch.

The encapsulated payloads will be transported to the Vehicle Assembly Building and loaded on to the H-IIA Launch Vehicle No. 17.

On April 30, the Venus Climate Orbiter “AKATSUKI” was mated with the Payload Attach Fitting (PAF,) which connects the AKATSUKI and the launch vehicle, at the Spacecraft and Fairing Assembly Building (SFA) at the Tanegashima Space Center (TNSC.)
The Small Solar Power Sail Demonstrator “IKAROS,” a co-payload of the AKATSUKI, has already been packed in the PAF.
The AKATSUKI will be encapsulated in the fairing, and transported to the Vehicle Assembly Building (VAB) to be loaded onto the H-IIA Launch Vehicle No. 17.

The Venus Climate Orbiter “AKATSUKI,” which left the Sagamihara Campus on March 17, arrived at the Spacecraft Test and Assembly Building 2 (STA2) in the Tanegashima Space Center at 5:30 p.m. on the 19th.

The Venus Climate Orbiter “AKATSUKI” left the Sagamihara Campus for theTanegashima Space Center (TNSC) on the evening of March 17.
The AKATSUKI will be delivered to the TNSC on the 19th. It will undergo final launch preparations there.

On March 12, the Venus Climate Orbiter “AKATSUKI” and the Small Solar Power Sail Demonstrator “IKAROS” were displayed to the media at the Sagamihara Campus.
The two payloads will be transported to the Tanegashima Space Center to be ready for launch.

The launch time and day of the H-IIA Launch Vehicle No. 17 (H-IIA F17) has been set for 6:44:14 a.m. on May 18. The H-IIA will carry the Venus Climate Orbiter “AKATSUKI,” the Small Solar Power Sail Demonstrator “IKAROS,” and four other small satellites to space.
The AKATSUKI special website opens today to keep you updated about its preparation status before its arrival to the Venus orbit. Please enjoy the site.

We have received many support messages from all over the world for the “AKATSUKI” message campaign, which was completed on January 10. The number of participants reached 260,214 people in total including those who registered through the Internet and those who signed up as a group from local areas, schools and science museums. We have also received messages from some celebrities. The messages will be printed on an aluminum plate, and attached to the body of the AKATSUKI. The satellite will then be transferred to the Tanegashima Space Center for launch preparations.

JAXA is currently holding a message campaign to carry your name and message to Venus by placing them on the Venus Climate Orbiter “AKATSUKI.”
We have so far received massages from some well-known people including Minister Sakihito Ozawa of the Ministry of the Environment, and Astronaut Koichi Wakata and his fellow crewmembers of the STS-127. We have also received a lot of messages from groups. In the case of a group message, the image of written messages of your group on paper will be printed as it is.
The deadline for accepting messages has been extended till January 10 (Sun.,) 2010 (Japan Standard Time.) Why don’t you send a message with your family members or friends during the New Year holidays?

On Nov. 27, the Venus Climate Orbiter “AKATSUKI” was revealed to the press at the Flight Environment Test Building at the JAXA Sagamihara Campus. Comprehensive tests on the AKATSUKI will be continued further to be ready for its launch.
The AKATSUKI Message Campaign has already passed the halfway mark, and less than a month remains to send in your messages. For those who have not sent us a message, we are looking forward to hearing from you! One unique feature of the campaign this time is that the image of written messages of your group on paper will be printed as it is in the case of a group message. Why don’t you send a group message, such as from a school or an office, on one piece of paper?

The Venus Climate Orbiter “AKATSUKI” (PLANET-C,) which is scheduled to be launched in Japan Fiscal Year 2010, will reach the orbit of Venus about half a year after its launch. It is scheduled to explore the Venus atmosphere for some two years. JAXA will deliver your name and message to Venus on this Venus explorer. We accept messages both from individuals and from a group such as a message from a school or a work place. Please participate in the message campaign by yourself, with your family, or with your friends.We are looking forward to receiving your thoughts. We will accept your messages up to December 25.

The PLANET-C project team started comprehensive tests in June. During testing, we first temporarily assemble all the parts to inspect the satellite comprehensively, disassemble it to check the components individually, then reassemble all the devices and components again to carry out various tests.

Photo: A container carrying the satellite structure is being brought into the test facility.

The satellite disassembly continues after the New Year holidays. The top photo show the removal of the 2μm infrared camera for observation (IR2) from the upper panel. Many pieces of equipment had been installed on the upper panel, but most of them were already removed. You can see the removed cameras on the table in the bottom photo. From the near side, they are the Ultra Violet Imager (UVI, a black camera under the blue plate), the 1μm Infrared Camera (IR1), the Longwave IR Camera (LIR, in a clear case) and the Lightening and Airflow Camera (LAC, wrapped in a golden sheet.)

On Dec. 23, we tested the observation cameras by turning all five cameras on and sending actual observation commands to them to check if all the cameras worked properly. The top photo shows that the 1μm infrared camera was lit. In the photo, the structure with a white disk-shaped antenna at the top is the main body of the PLANET-C. As the solar array paddles were removed, the white round antenna that had been covered before was revealed. The cameras were attached at the right edge on the near side. There is a bright light instead of Venus in front of the cameras, thus a silhouette of the satellite is clear on the back wall.

On December 25, various tests were completed, and the satellite was started to be disassembled. The bottom photo shows that the upper panel was carefully being removed from the satellite’s main body.

Since October 1, 2008, JAXA has been carrying out the first integration test for the PLANET-C. The test takes about three months to build up the satellite with most of the parts of the flight model into almost the launch configuration. The test is being held in the big clean room, and it is a very important test to verify mechanical and electric integration and function in the quasi launch configuration. It has been spectacular to witness all the individually developed parts and observation devices collected in one room to be set up as the satellite.
The top photo shows the testing scene, and the upper panel to which many parts including the observation equipment are attached is on the right hand side, and the black cylinder on the left is a thrust tube that supports the propellant tank. On December 8 and 9, the satellite was built up. The upper panel and lower panel of the orbiter were attached, and it now looks like a satellite. After performing various tests with the integrated satellite, it will be disassembled again at the end of this month, then each part will be adjusted, if necessary, and individually tested further.
The lower photo is the completed PLANET-C. Four observation cameras are installed on the right hand side of the satellite. They are the Long-wave IR camera, the Ultraviolet imager, the 1µm camera, and 2μm camera (from the top to the bottom.) The object looks like an arm holding the head is a folded solar array paddle.

On July 3, 2008, JAXA held the “Selection Committee Meeting for Small Secondary Payloads Launched with PLANET-C,” and the following four satellites were chosen as candidates for a piggyback launch with PLANET-C by H-IIA.

Among them, UNITEC-1 will be the world’s first satellite developed by a non-space organization to travel to Venus.

One of the five cameras aboard the Venus Climate Orbiter “PLANET-C” is the “IR2,” whose observation target is infrared rays that are about two micron in wavelength. It aims to measure the high-temperature atmosphere of Venus under thick clouds, its movement, and distribution of its trace components. In other words, the IR2 is a camera that can see through the real surface of Venus. The IR2 is made of materials suitable for infrared ray observations (manufactured by Nikon) and its photo-taking device (element) which is equivalent to a CCD in a digital camera is made of Platinum Silicide (PtSi) element (manufactured by Mitsubishi Electric.)

The PtSi element is one million pixels (1024 x 1024). We are very proud of its high performance, which is far superior to commercially sold digital cameras or video cameras. It can work stably in the harsh environment of space with an excellent ability to capture both dark and bright objects (dynamic range) and a very high accuracy of measurement (linearity.) Currently, one million pixels is the highest level for this type of camera.

The PtSi detector shown in the photo is a trial piece. The one million pixel (1024 x 1024) light receiving surface is about 17 mm x 17 mm in size and attached to the IC package. We have already acquired satisfactory results for this element through a cooling evaluation test. In May 2006, we began to manufacture the prototype and flight model elements by slightly modifying the design of the trial piece.

The “IR2” and the other onboard infrared camera, “IR1,” are the main cameras of the orbiter. Although the two cameras target different observation wavelength ranges, their elements are almost the same. In addition to the lenses and elements, the camera unit itself, equipped with a cooling device for both the IR1 and the IR2, is developed by a Japanese precision equipment manufacturer (Sumitomo Heavy Industries, Ltd.) thus they are being developed 100% domestically.

It is not easy for Japan to challenge the space development field by itself, as Japan lags behind Western countries. Still, we believe that we can accumulate knowledge through the challenge to sophisticate our own advanced technologies and promote our cutting-edge space science. Therefore both the engineers and scientists are working together for this development.

The Venus explorer, Planet C, was developed to observe the atmospheric movement of Venus by taking images of lights in various frequencies using five onboard cameras. By doing so, we try to elucidate the “super rotation of the atmosphere” that is the biggest mystery of meteorology in the solar system. Super rotation is a phenomenon where the atmosphere of Venus rotates about 60 times faster than Venus’ rotation. (The Venus rotation period is 243 days, whereas the atmosphere is 4 days.) The IR1 Camera, designed to capture infrared lights in one micron range wavelength, can carry out observations both day and night to contribute to the clarification of the mystery.

During the day time, the IR1 will detect atmospheric movement in lower clouds, catching the deranged light of the Sun from the cloud layer (45 to 65 km) covering all of the surface of Venus. In the night, we plan to make it observe material compositions on the surface of Venus and look for an active volcano. It is well known that there are traces of volcanic activity on Venus, but no active volcano has been found yet. The observation team has high expectations of finding an active volcano, because, if we succeed, we can obtain clues to learn about the inside of Venus and its evolution.

When we observe the night side of Venus, strong sunlight obstructs observation activities. Therefore, a sun shield cylinder plays an important role to protect our observation data by cutting off sunlight. The photo shows the testing of a new sun shield cylinder consisting of square and round shaped boards (in the big darkroom at the Usuda Deep Space Center in Nagano.)

The Venus probe “PLANET-C” is equipped with five cameras, one of which is the first lightening and airglow camera (LAC) for a planet-probing mission in the world. The LAC can shoot 50,000 times per second using its high-speed mechanism to ensure it captures the precise moment when lightning strikes. (People think that we can see lightening flashes with our naked eyes, but it is actually through persistence of vision.)
The camera also has an “automatic event detection” function to determine if lightening really took place. This function is a unique feature to sort out only “real” lightning data from a large amount of trial image data.
In order to pass very strict weight constraints, the LAC design was modified in the fall of 2004, and we successfully reduced its weight by more than 70 percent (from about 5.2 kilograms to about 1.5 kilograms.) We have been verifying the possibility by using a prototype to change the image-pickup element (pixels) from MCP (Micro Channel Plate) to APD (Avalanche Photodiode), which is a more reliable and durable element.
The development team holds high expectations that the LAC will end a dispute over the “existence of lightning and electric discharging on Venus” which has been debated for more than 20 years.

Outline of the Lightning and Airglow Camera (The latest version, Spring 2005)

1) LAC before design change (left)
2) External view of the LAC after design change (center) and the optical system (right)
As the new design does not have a hood to shield it from sunlight or reflections from clouds over Venus, it will carry out observations only when the PLANET-C is in the night side of Venus.
3) Arrangement of filters on the light receiving side
By dividing the detector’s light receiving side in five, five kinds of filters of which each penetrates specific wavelengths of light, are attached directly to the image-pickup elements (pixels) to shoot different observation targets pixel by pixel. In the new design, we do not need the filter rotation mechanism, and that greatly contributed to make the camera lighter.

The Planet-C project, which was officially started this past April, is now at the stage of designing a prototype model of a probe.

Planet C is equipped with five special onboard cameras for measuring infrared lights and ultraviolet rays in various wavelengths to observe from the surface to the upper atmosphere of Venus. For observation purposes, it is challenge to keep the inside temperature of the probe cool. Infrared lights are also known as “heat rays”, and a device may not be able to measure properly if it becomes too hot.

Venus is 40 million kilometers closer to the Sun than the Earth. Therefore, the prerequisites to control the thermal environment for a Venus probe are far stricter than for a satellite cycling around the Earth. More specifically, the project faces challenges to design a more efficient method to release heat from the probe into space (thermal structure design) and to control the heat generated by onboard equipment. We need to adopt some parts that do not have any history of use in the space development area, thus we are carefully carrying out radiation exposure tests.

The development team, consisting of research institutes and manufacturers across Japan, is working hard to achieve future applications for Earth observation missions.

* Photo : The photo is a test image taken by a model device for evaluating the performance of one of the onboard cameras, the mid-infrared camera. The photographed subjects are two black boards whose temperatures are slightly different. The temperature difference is clearly shown in the photo. On the upper left side, you can see a camera called a “non-cooling bolometer” with a new detector that enables it to perform infrared measurements without being cooled down. Thanks to this new detector, the camera becomes much smaller than the conventional one that requires a system to cool a detector. We expect that the camera will elucidate the temperature and movement of clouds around Venus.

The PLANET-C Project Team has been engaging in the initial design of the probe and development of a set of observation cameras for Venus. Many of the cameras are embedded with high pixel infrared sensors. Therefore, many tests, including radiation exposure, were carried out to verify their reliability in a space environment and to maximize their performance.
In order to acquire emissions of thin infrared or thunder lights from the atmosphere or ground surface on the night side of Venus, the development of a high-performance “hood” is critical to eliminate the impact of strong sunlight. It is also imperative to maintain a cool temperature inside the probe to accurately measure infrared lights that are called “heat rays”. A more proficient design and structure is required for the Venusian orbit probe to dissipate heat to space as it travels much closer to the sun than earth orbit satellites.
The designing is almost completed, and we will begin to develop and manufacture the trial model of the probe in April 2004. We are now fully prepared for moving to the next step.

* Photo : Infrared cameras under development. Universities and research institutes, including Hokkaido University, Tohoku University, National Institute of Polar Research, Tokyo University, Osaka Prefecture University, and Kumamoto University, participate in the development of scientific observation equipment such as a set of infrared cameras.