posted 08-03-2022 06:06 PM               

Korea Pathfinder Lunar Orbiter (KPLO) Danuri

A test lunar orbiter (KPLO, Korea Pathfinder Lunar Orbiter), the first Korean lunar probe, is an unmanned lunar probe expected to carry out the mission of lunar observation while flying at an altitude of 100km over the Moon.

The test lunar orbiter (KPLO) consists of the main body with a width, length, and height of 1.82m, 2.14m, and 2.29m, respectively, and six payloads. The major project details of the test lunar orbiter involve the development of the main body and payloads of the test lunar orbiter, construction of a deep-space ground station, phase 2 preceding research, and international collaboration with NASA.

The project is carried out with the cooperative system in which KARI oversees the system, main body, and ground station with the participation of six major Korean research institutes and NASA of the U.S. It will be equipped with NASA payloads and carry out missions such as orbiter tracking, communication support, deep-space navigation service support, etc.

Technologies required for Lunar Orbit Exploration

The test lunar orbiter (KPLO) is scheduled for launch on board the U.S. SpaceX’s Falcon 9 launch vehicle in August 2022. After its launch, the test lunar orbiter (KPLO) will shoot toward the Moon using the lunar orbit transfer method (BLT/WSB), which approaches lunar orbit by using the nearby astrophysical gravity of the Sun and Earth.

The test lunar orbiter (KPLO) is expected to commence lunar surface filming after going through its initial testing upon entry into lunar orbit.

Six payloads developed by Korean research institutes & NASA

The test lunar orbiter (KPLO) will carry a total of six payloads. The orbiter will contain five payloads developed by Korean universities and research institutes including KARI and one payload from NASA.

Korean universities and research institutes are developing a high-resolution camera for exploring the proposed landing site for lunar landing module, a polarized camera to analyze the lunar surface particles and spacecraft’s effect, and a lunar magnetic field-measuring instrument to measure the magnetic field intensity around the Moon for studying the cause and process of Moon formation.

The Korea Institute of Geoscience & Mineral Resources, which will measure the gamma-ray spectrum for resource exploration of the lunar surface, has been developing a gamma-ray spectrometer for identifying the elements constituting the lunar surface and its distribution pattern, while KARI is developing a 5m-grade high-resolution camera filming the proposed landing site for the Korean lunar probe.

The polarized camera being developed by the Korea Astronomy & Space Science Institute will be used to film the image of the entire lunar surface and capture polarized images of areas except for the polar region. In addition, it will designate the proposed landing site for the lunar probe by using the filmed images and examine the types of materials and particle sizes on the surface of the Moon.

Kyunghee University is developing the lunar magnetic field measuring instrument, a magnetometer for measuring the magnetic force 100km above the surface of the Moon. The gamma ray spectrometer can identify the ingredients and distribution patterns of elements constituting the lunar surface. It is being developed by the Korea Institute of Geoscience & Mineral Resources. The Electronics & Telecommunications Research Institute (ETRI) has been developing the space Internet test equipment for testing the delay-tolerant network. NASA’s ShadowCam will perform the reflectivity mapping of permanently shadowed regions on the surface of the Moon to find the evidence of water.

Going to the Moon with BLT/WSB method

The orbit for going to the Moon broadly consists of Direct Transfer, 3.5 Phasing Loop Transfer, BLT (Ballastic Lunar Transfer), etc.

The Direct Transfer method previously used by the Apollo program requires time within about five days. It directly arrives on the Moon after its launch from Earth. The 3.5 Phasing Loop Transfer used by India’s Chandrayaan program is a method of entering lunar orbit after revolving several times around the Earth in a long elliptical orbit. BLT/WSB method entails flying to the L1 Lagrangian point between the Earth and Sun, which was designed to minimize the space probe’s fuel consumption.

After launch, KPLO will be separated from the launch vehicle after entering the Transfer Orbit, an elliptical orbit. Subsequently, after making the solar panels face the Sun, the solar panels will be fully deployed by automation. Then, the process of raising its orbit by liquid apogee engine (LAE) firing occurs in order to enter the drift orbit from transfer orbit.

Once the satellite gets into position, the engine fires a total of five times and ascends into a circular orbit (drift orbit) from an elliptical one. And then, by using orbit information and the satellite-installed star sensor, it acquires its position facing the Earth, and finally reaches satellite mission altitude.

posted 08-04-2022 09:51 AM               

SpaceX is targeting Thursday, August 4 for launch of KPLO to a ballistic lunar transfer orbit from Space Launch Complex 40 (SLC-40) at Cape Canaveral Space Force Station in Florida. The instantaneous launch window is at 7:08 p.m. ET (23:08 UTC), and a backup launch opportunity is available on Friday, August 5 at 7:00 p.m. ET (23:00 UTC).

The Falcon 9 first stage booster supporting this mission previously launched Arabsat-6A, STP-2, COSMO-SkyMed Second Generation FM2, and two Starlink missions. After stage separation, the first stage will land on the Just Read the Instructions droneship, which will be stationed in the Atlantic Ocean.

posted 08-04-2022 10:20 PM               

Danuri launches as scheduled

The Ministry of Science, ICT and Future Planning (Minister Jong-Ho Lee) dispatched the lunar probe 'Danuri' on August 5 (Fri) around 08:08 (local time on August 4 (Thursday) at 19:08) Cape Canaveral, Florida, USA. The space force base said it would launch as scheduled.

At the Danuri launch site, Cape Canaveral, the US Space Force Base successfully completed all pre-works such as functional check, fuel injection, and assembly with the launch vehicle for about a month.

Danuri will be separated from the projectile approximately 40 minutes after launch, and will communicate with the ground station for the first time approximately 20 minutes after launch (about 1 hour after launch).

After that, it is expected that the Korea Aerospace Research Institute (Director Sang-ryul Lee) will be able to check whether Danuri succeeded in entering the lunar transition trajectory at around 13:00 to 14:00 (5 to 6 hours after launch) by analyzing the launch vehicle separation information.

posted 09-06-2022 09:57 AM               

Confirmation of normal performance of Danuri second trajectory correction operation

Korea Aerospace Research Institute carried out the second trajectory correction operation of Danuri as planned, around 5 p.m. on Friday, September 2nd.

The second trajectory correction maneuver is an essential process to minimize the fuel consumption required for Danuri's Earth-Moon navigation and to arrive on the moon normally in accordance with the mission schedule.

The Aerospace Research Institute was originally scheduled to confirm the final result of the second trajectory correction operation around 5 p.m. on September 4 (Sunday) through the analysis of the trajectory information for about 48 hours, but after about 25 hours, on September 3 (Saturday), around 6 p.m. they were able to confirm final success. The reason that we were able to confirm the final result sooner than expected is because, in addition to the analysis experience of the first trajectory correction operation, the trajectory information after the second trajectory correction operation came out almost identical to the predicted one.

As the second trajectory correction operation was successfully carried out, the originally planned next trajectory correction operation (September 16) will be omitted.

posted 12-17-2022 09:32 AM               

Danuri begins entering lunar mission orbit

The Ministry of Science and Technology and the Korea Aerospace Research Institute that launched the lunar orbiter Danuri announced that the first lunar orbit entry maneuver was being carried out at 2:45 a.m. on Dec. 17, 2022 (2:45 p.m. EST or 1945 GMT on Dec. 16).

Danuri flew a total of 5.94 million km (cumulative) along the Earth-Moon trajectory for about 4.5 months after launch on Aug. 5, and came close to a distance of about 108 km from the moon on Dec. 17. After that, from December 17th to December 28th, Danuri will go through a total of five mission orbit entry maneuvers* to settle in the lunar mission orbit (100km above the moon).

In particular, this first entry maneuver is the most important maneuver to ensure that Danuri is stably captured by the moon's gravity and does not pass the moon. During this process, the thruster must be operated for about 13 minutes to reduce the speed of Danuri from about 8,000 km/h to 7,500 km/h, while accurately reaching the target position. This is a highly difficult task to enter the Danuri (7,500-8,000 km/h), which moves faster than a bullet, into the orbit of the moon, which is moving at the speed of a bullet (about 3,600 km/h). The results of the first entry maneuver are scheduled to be drawn on Dec. 19 after data analysis. 

Afterwards, it will go through the second to fifth entry maneuvers (Dec. 21 to Dec. 28), and finally, on December 29th, Danuri's lunar mission orbit will be confirmed.

posted 01-05-2023 09:24 PM               

Earth-moon photographed by Danuri

Korea Aerospace Research Institute released Earth-Moon photos taken by Danuri.

Danuri is currently carrying out work such as checking the performance of the payload and adjusting errors, and since February, full-fledged scientific research such as moon science research (photography of the lunar surface, polarization imaging, imaging of permanent shaded areas and observation of magnetic field and gamma rays), space internet technology verification, etc. technical missions will be performed.

Dec. 24, 2022, 344 km above the moon:

Dec. 28, 2022, 124 km above the moon:

Dec. 31, 2022, 119 km above the moon:

Jan. 1, 2023, 117 km above the moon:

posted 04-08-2024 09:05 PM               

NASA's LRO Finds Photo Op as It Zips Past SKorea's Danuri Moon Orbiter

NASA's LRO (Lunar Reconnaissance Orbiter), which has been circling and studying the Moon for 15 years, captured several images of Korea Aerospace Research Institute's Danuri lunar orbiter last month. The two spacecraft, traveling in nearly parallel orbits, zipped past each other in opposite directions between March 5 and 6, 2024.

The dark spot centered in the bottom third of this image is the Korea Aerospace Research Institute's Danuri orbiter, smudged because it was traveling quickly in the opposite direction of NASA's LRO (Lunar Reconnaissance Orbiter) when LRO snapped the photo. At the time, Danuri was orbiting 5 miles, or 8 kilometers, below LRO's orbit, and LRO was about 50 miles, or 80 kilometers, above the Moon's surface. This image covers an area about 2 miles, or 3 kilometers, wide. (NASA/Goddard/Arizona State University)

LRO's narrow angle camera (one in a suite of cameras known as "LROC") captured the images featured here during three orbits that happened to be close enough to Danuri's to grab snapshots.

At the first imaging opportunity, LRO was oriented down 43 degrees from its typical position of looking down at the lunar surface to capture Danuri (streaked across the middle) from 3 miles, or 5 kilometers, above it. (NASA/Goddard/Arizona State University)

During the next encounter, LRO was closer to Danuri, about 2.5 miles, or 4 kilometers, and oriented 25 degrees toward it. (NASA/Goddard/Arizona State University)

Due to the fast relative velocities between the two spacecraft (about 7,200 miles, or 1,500 kilometers, per hour), the LRO operations team at NASA's Goddard Space Flight Center in Greenbelt, Maryland, needed exquisite timing in pointing LROC to the right place at the right time to catch a glimpse of Danuri, the Republic of Korea's first spacecraft at the Moon. Danuri has been in lunar orbit since December 2022. Although LRO's camera exposure time was very short, only 0.338 milliseconds, Danuri still appears smeared to 10 times its size in the opposite direction of travel because of the relative high travel velocities between the two spacecraft.

For the final photo, LRO was reoriented by 60 degrees to catch a glimpse of Danuri when it was 5 miles, or 8 kilometers, below it. This image pair was corrected for viewing geometry, and, on the right, the Danuri pixels were unsmeared and the image stretched to highlight the Korean spacecraft. The image was rotated 90 degrees so the surface would look like something a person would see looking out the window. (NASA/Goddard/Arizona State University)