Issue 122

2-7 June: China is maneuvering both SJ-21 (49330) and SJ-25 (62485) in order to conduct the world’s first refueling experiment in Geosynchronous orbit. As of 6 Jun the satellites are on orbital trajectories will have them in close proximity on ~11 June. China has stated SJ-25 is an on-orbit service test vehicle, specifically a refueling satellite. SJ-21 captured and hauled away a piece of space debris in GEO back in January 2022. The US has placed TWO of its GSSAP satellites (USA 270 <41744> & USA 271 <41645>) in position to observe. Watch COMSPOC Video Link of maneuvers from 2-5 June. See Jack Anthony’s explanation of “How to Rendezvous With Another Satellite.” China appears to be following this playbook exactly!

Timeline:

• 2 Jun: the Joint Commercial Operations Cell reported that SJ-21 raised its average altitude ~296km, initiating a westward drift of ~4°/day. SJ-21 and SJ-25 remain plane matched (inclination 10.5 deg & RAAN 42.6 deg). At the time of the maneuver SJ-21 was at 133.16°E and SJ-25 was at ~120°E.
  • In addition to changing its SMA, China also maneuvered to change SJ-21’s eccentricity (orbit shape) to more closely match that of SJ-25.
• 4 Jun: SJ-21 decreased its SMA ~311km, eliminating its westward drift and parked the satellite at 127.5°E. SJ-25 remained at ~120° East.
• 6 Jun: SJ-25 lowered its SMA 119km to initiate a 1.5°/day eastward drift (and toward SJ-21). At this drift rate SJ-25 and SJ-21 will be in close proximity in ~5 days (11 June 2025).

– Prior to 2 June 2025 the last time China maneuvered SJ-21 was in July 2023.

– From COMSPOC: “SJ-21 used a total of ~25 m/s of delta V and it got roughly halfway to SJ-25. Odd that they would stop — meaning, if they were only going to go halfway, why go so fast and use so much fuel? Perhaps the remaining fuel onboard 21 is not a concern.”

Editor’s Note: For those Thank you to the COMSPOC team for their fantastic collaboration!

29 May: China launched a Long March-4B containing the Shijian-26 (SJ-26) (64199) satellite from Jiuquan. China releases few details regarding its Shijian experimental satellites, in this case official sources noted a remote sensing mission stating, “the satellite is mainly used for national land surveys, environmental management and other fields, providing information services to support national economic development”. SJ-26’s orbit inclination and average altitude is typical for imagery related satellites and is nearly identical to the orbit of China’s 5 Gaofen-11 imagery satellites. Launch Video.

– SJ-26 is in a sun-synchronous orbit (SSO) with an average altitude of 496.6km and an inclination of 97.5°.

– SJ-26’s orbit closely resembles that of the Gaofen-11 series of high resolution optical imagery satellites (43585, 46396, 49492, 54818, 60249). All 5 of the Gaofen-11 satellites were also launched on a LM-4B, however the launches were from Taiyuan and not Jiuquan.

– Like SJ-26 all of the GF-11 satellites are in sun-synchronous orbits and inclined at ~97.5° with an average altitude of ~496km.

– GF-11 01 has not maintained its orbit since August 2023 and may have reached its end of life. Its average altitude has slowly declined over the past 2 years and the satellite now has an average altitude of 436km (see graph below).

– China’s official description of GF-11 is also very similar to that used for SJ-26: “(GF-11) will be used in a variety of fields including land surveys, urban planning, road network design, crop yield estimation and disaster relief”.

– Previously, Chinese officials have stated that of the 14 Gaofen satellites variants “1-7 are civilian satellites, and 8-14 are military satellites.” The same official also noted “The best satellite in the U.S. is Keyhole. Its resolution is 0.1m. Our Gaofen 11 can also meet this standard.”

– Without additional information, such as a high resolution image, the mission and capabilities will remain unknown. SJ-26 was developed by the Harbin Institute of Technology while GF-11 satellites were made by CAST.

-Placing SJ-26 in a similar orbit as the GF-11 satellites may provide China with an opportunity to compare results as they test whatever new technology is on the SJ-26.

https://www.youtube.com/watch?v=6tlSQUHTsp0

20 May: China launched a Long March-7A with the ZhongXing-3B (ChinaSat-3B) (64062) communications satellite from Wenchang. According to official sources, the satellite entered the planned orbit and “will provide voice, data, radio and television transmission services”. After spending ~10 days in GTO, Chinese space operators circularized ZhongXing-3B’s orbit in GEO and the satellite is now over the equator at 167.3°E. At its current location ZhongXing-3B is the furthest East of any of the ZhongXing/ChinaSat satellites. Launch Video.

– ZhongXing-3B is in Geostationary orbit and is inclined 0.0°. It is currently 3.9° further east than Zhongxing-19 which China launched in 2022.

– Zhongzing-3B’s location will likely provide greater and more resilient connectivity in the Western & Central Pacific regions.

– Per Andrew Jones: “ChinaSat satellites are generally described as commercial or civilian assets. However, some of them-particularly the lower-numbered in the series-likely have military or intelligence applications, such as secure communications for the People’s Liberation Army (PLA). The absence of public information and imagery raises the possibility that ChinaSat-3B serves military users.”

https://www.youtube.com/watch?v=b4nVAxz0I88

5 Jun: China launched a Long March-6A with the fourth group of Guowang (SatNet LEO Group 04) satellites from Taiyuan. According to official sources, the satellites entered the preset orbit successfully. Consistent with previous Guowang launches, Chinese officials did not provide information on the number of satellites, nor any details about the satellites’ capabilities. The 18 Space Defense Squadron has cataloged 5 satellites (64283-64287) and 1 LM-6A Rocket Body. Nice going 18 SDS! Launch Video.

– With this launch there are now 34 satellites in the operational Guowang constellation. Additionally, China has launched 14 Guowang test satellites. (see table and graphic)

– Per Andrew Jones report: “The China Academy of Space Technology (CAST)…stated in December (2024) it had developed large and small satellite platforms for Guowang, without disclosing functional differences.”

-Given the maximum lift to LEO capacity of the LM-6A of ~8,000kg these 5 satellites are likely the smaller variant.

• Two of the four Guowang launches used the much larger LM-5B (max capacity to LEO of 25,000kg) carrying 10 Guowang satellites per launch. These were likely the larger Guowang variants.
• The other Guowang launch used the LM-8A (max capacity to LEO of 7,000kg) which carried 9 satellites to LEO. These were likely the smaller variant.

– All of the Group 04 satellites are in 86.5° inclined orbits and are at an average altitude of ~1,003km. They will likely increase their average altitude to 1,067.9km to match the 20 other Guowang satellites in 86.5° inclined orbits.

• The two previous launches to 86.5° both used the LM-5B (Groups 1 & 3). The satellites increased their orbits to 1,067.9km. The first group required 109 days to reach operating altitude while the second group required only 37 days.
• The 9 satellites launched with the LM-8A (Group 2) are in a 50.0° inclined orbit and are at a slightly lower average altitude of 1,149.3km. They required 77 days to reach operating altitude.

– The Group 4 satellites have a ~32.3° east RAAN offset with the Group 1 satellites. The Group 1 satellites themselves have a 30.4° east RAAN offset with the Group 3 satellites. (see graphic)

– Per Andrew Jones:

• “The China Satellite Network Group Co., Ltd. (‘China SatNet’), established in April 2021, is responsible for Guowang. The constellation is based on China’s filing with the International Telecommunication Union (ITU) in September 2020 for a total of 12,992 satellites. According to the filings, two sets of satellites-GW-A59 and GW-A2-are outlined. These will operate at altitudes below 500 km and between 600—1145 km respectively, using a mix of orbital planes.
• “According to an August 2024 issue of the China Aerospace journal, the Guowang constellation is expected to adopt new-generation dynamic beam control and optical inter-satellite links, enabling high flexibility and customization. The satellites will serve both government and civilian users, providing broadband connectivity and tailored data services.”

https://www.youtube.com/watch?v=1ikczXImyDg

3 Jun: China is in the process of maneuvering its three Yaogan-40 02A-C (63918-20) satellites to form an equilateral triangle formation. The satellites launched into the same 86.0° inclination as the YG-40 01A-C triplets (57830-32). This inclination will allow China to monitor the Arctic and Antarctic regions. The two sets of triplets are not co-planar as the YG-40 02 satellites are offset ~72° west of YG-40 01.

Two of the satellites (63918 & 63919) increased their average altitude after launch from 802km to ~850km which is the operating altitude of the YG-40 01 triplet. The remaining satellite (63920) decreased its average altitude from 802km to 787km and is drifting west relative to the other two satellites. Once 63920 reaches the desired RAAN offset Chinese space operators will increase its average altitude to join the other two satellites. Once co-altitude the satellites will maintain their relative distance from one another forming an equilateral triangle.

The RAAN offset for the YG-40 01 triplets is 1.3°. The current RAAN offset for YG-40 02 is only 0.2°. At their current rate (daily RAAN differential is .015°/day) YG-40 02 will achieve 1.3° RAAN differential in ~73 days or 15 Aug 2025. Stay tuned to see if our prediction proves correct.

The United States has accused Russia of conducting on-orbit counterspace testing in the past. Testing thus far has not resulted in the creation of space debris. Below is an excerpt from the most excellent Secure World Foundation (SWF) 2024 Global Counterspace Capabilities Report describing the activities of Cosmos 2519 and its sub-satellites, Cosmos 2521 & Cosmos 2523, from July 2017 – June 2018.

Cosmos 2519

• On June 23, 2017, a Russian Soyuz 2-1v rocket was launched from Plesetsk with two military payloads.
  • One payload was rumored to be the first of the new series of military geodetic satellites, used to create extremely precise maps of the Earth’s shape and gravitational field.
  • Russian officials declared that the launch also included a “space platform which can carry different variants of payloads” which was designated Cosmos 2519 (2017-037A, 42798).
• In late July and early August, Cosmos 2519 made a series of small maneuvers. Publicly available information strongly suggests that Cosmos 2519 had a remote sensing mission.
• On August 23, 2017, Russian officials announced that a small satellite, designated Cosmos 2521 (2017-037D, 42919) had separated from the platform and was “intended for the inspection of the condition of a Russian satellite.”
  • Russia reported that the satellite-inspector completed a series of proximity operations experiments and returned to the Cosmos 2519 host satellite on October 26.

• On October 30, Russia announced that another small satellite, Cosmos 2523 (2017-037E, 42986), separated from Cosmos 2521 and would have a satellite inspection function but to date, it has not been proven to approach other satellites.
• Jonathan McDowell calculated that Cosmos 2523 was released at a relative velocity of 27 meters per second (60 miles per hour).
• Comments from senior US military leadership suggest they consider the deployment of Cosmos 2523 to have been an ASAT test, given its relatively large deployment velocity.
• Throughout March, April, and June 2018, Cosmos 2519 and 2521 conducted several RPOs of each other.
  • After March 2018, Cosmos 2519 and Cosmos 2521 did not maneuver to approach any other space objects but made small adjustments to their orbits, likely to forestall natural orbital decay.
• Cosmos 2521 eventually re-entered the atmosphere on September 12, 2019 and Cosmos 2519 re-entered on December 23, 2021. As of February 2024, Cosmos 2523 remains in orbit.

This essay will introduce the process of a “chaser” spacecraft (maybe a refueler servicing vehicle) goes through to arrive at the “target” spacecraft (the one who ordered the refueling). The terms chaser and target have been used by NASA way back as they planned and executed rendezvous, then loitered around the other spacecraft, that’s called proximity operations, and then they would dock. Some call this ZPO, zero prox ops. This process involves maneuvering the chaser and hopefully the target is cooperative and not maneuvering without telling you.

The chaser’s orbital elements provide information into how the rendezvous mission progressing If you are not aware of the target, following this trend will help resolve that. It’s the change and matching of the chaser’s elements to the target’s elements that give insight into how the process is moving along. In the end, if the chaser is to dock with the target, then the orbital elements must match. There are three phases to completing a RPO and then ZPO. While the chaser’s maneuvers may not always follow the expected flow of these phases, they provide a framework to follow along. Here below is a table that summarizes the 3 phases. Give it a review and study before reading on, it will be helpful.

Let’s look at each phase and go a little deeper to give you insight into what’s going on.

Orbit Plane Matching: Plane matching usually occurs early in planning and executing a mission. The launch vehicle usually does it all, you launch right into the orbit plane of the target (see Russia’s Kosmos 2558 and 2576). But there can be errors in that insertion and thus orbit plane matching maneuvers are needed. Below is a simple illustration (all my drawings are simple😁) that shows the red and blue orbits have different inclinations and RAANs. So, the task at hand to match orbit planes would be to execute a Delta V where that star is and get the orbit planes matched to have same inclination and RAAN. A really important step to ensure when you get close for proximity operations you are not zig zagging back and forth.

The chaser can do a series of small orbit plane adjust maneuvers to incrementally get the orbit planes aligned. As you all remember from the Orbital Element Series of articles I wrote, the orbit plane is characterized by the inclination and RAAN. The amount of Delta-V to align inclination only gives us some basic rules of thumb. In GEO, 53 m/s of Delta-V is needed to change or correct 1 degrees of inclination, for LEO it’s about 115 m/s. But remember, you got to also get the RAAN lined up. That can be costly in propellant. Here’s an example: You launched into a 97.4 degrees incline LEO orbit. Nailed the inclination. But, the RAAN is not aligned, it’s off by 1.5 degrees. How much Delta-V do you think is needed to fix that? Hummmm? Well, its 197.5 m/s, wow! Now, get ready for some learning, what if the inclination was 28 degrees. Is there a difference in what’s needed to fix the 1.5-degree error in RAAN? Yup, it’s only 97 m/s. Still, a lot. So, orbit plane matching usually is the launch vehicles chore, but if you need to tweak things to get the orbit planes aligned, that can cost you fuel (and time making PowerPoints to explain what’s going on…LOL).

Orbit Shaping & Alignment: Normally mission planners like to have the long axis of the orbits matched, this is called the line of apsides. It enables efficient maneuvering. This can be a very subtle stage, usually the orbits are so near circular this phase may not occur. Orbit shaping is reflected in the eccentricity and argument of perigee matching. Hopefully the launch vehicle did its job getting things properly inserted into orbit. Of course, if the target starts playing games and maneuvering, then this problem gets tougher. The illustration on the next page shows that the red dashed orbit and the blue orbit do not have their lines of apsides lined up. Some planners would want to execute a maneuver to get them aligned to support more efficient maneuvering.

Orbit Phasing: This is my favorite phase. This is where you get to close in on the target and hang out with them or better yet, dock and refuel them. This phase is usually seen as where the chaser orbit is being adjusted and we see changes in its orbit’s apogee and perigee. They are fiddling with the semi-major axis and getting the approach going, perhaps slowing down the relative closer rate. As semi-major axis getting close to a match, chances are the true anomaly is also closing in. Match them up and you can reach out and shake hands or get set for the dock and refueling. Here’s a cool rule of thumb I think you’ll enjoy knowing and sort of relates to phasing. For LEO Earth orbits, there is a 10:1 rule, my friend James Oberg at NASA/JSC came up with it. Here’s what it means. If you are 1 Km below your target orbit and you are plane matched and circularized, then you will advance 10Km forward each orbit period. Thus 10:1. So, let’s say you are 5 Km below and 150 Km behind. Let’s say your orbit periods are really close and 90 minutes. OK, so when will you be right underneath the target? Well, use the 10:1 rule. Each orbit you scoot ahead relative to the target 50 Km (5 Km times 10). So, we are 150 Km behind, and guess what? In 3 orbit or 4.5 hours we can look “up” and see the target. Pretty cool, the 1- to 1 rule of thumb by James Oberg. Yay for him!

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Well, there you have it. The 3 phases of RPO and some details as to what’s going on. You may ask, how does Jack know this stuff? Well, two folks play a BIG role in helping me understand and get all enthusiastic about RPO. Dr Chirold Epp helped me in the early 1980’s. While at Johnson Space Center I’d meet with Dr Epp and he’d tell me all the cool things Shuttle would be doing with regard to RPO. He helped me understand the math and art to all this. Then Mr. A. Clark Keith III came along in 1989 as my Aerospace Corporation advisor for the famous TAOS space mission that flew 1994-2000. I got to know Clark and one of his finest hours (or years) was the XSS-11 RPO test mission that flew 2005-2007. Clark was the Flight Director and he wrote up notes that comprised a “how to” handbook for RPO. Just before his battle with cancer took him from us in 2013, Clark wrote up his notes and gave them to his colleague Jim Baker to publish. I met with Clark just before he passed and he said “Jack’s I’m writing everything down, make sure you read and live it.” Clark’s experience, insight, and ability to explain things was awesome and helped all of us know the ways to achieve RPO. He is the Father of Military RPO. He played a huge role in planning the ANGELS mission and many more space test missions. I miss Clark and thank him. DO YOU HAVE A MENTOR HELPING YOU UNDERSTAND YOUR AREA OF RESPONSIBILITY? I BET YOU DO.

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Here’s a photo of Clark and I in 2011 at the USAF Academy FalconSAT Operations Center. He loved coming to meet with the cadet’s and talk spaceflight!