mission profile:
soft landing is one of main objectives of luna-25
DISD-LR ДИСД-ЛР
The soft landing of the station should be provided by a Doppler speed and range meter (DISD-LR) developed by the Vega Concern (part of the Rostec State Corporation's Roselectronics holding). The DISD-LR device is being created in the conditions of import substitution, the developers note.
According to the original plan, Luna 25 was supposed to be launched in 2014. However, various reasons provoked delays one after another. The last big postponement (from 2021 to 2023) was caused by the malfunction detected (80% accuracy in readings) in the Doppler speed and range meter (DISD-LR) during the tests. Being an important part of the soft landing system, this device couldn’t be ignored, and its insufficient accuracy may cost a mission. The repeated tests of DISD-LR and subsequent changes of the lander’s software caused a delay for almost two years
22 x 13x 2Slotted waveguide antenna array，slot length 20mm est.(2.4 GHz?). Slot array, matlab, slideplayer
Moon dust: the
The Apollo 15 crew noted that landing radar outputs were affected at an altitude of about 30 ft by moving dust and debris. The dust coated the television camera lens and produced a halo in photographs. In the Apollo 12 mission, the landing velocity trackers gave false readings when they locked onto moving dust and debris during descent. All the Apollo landings were manually done to avoid wrong manoeuvres due to faulty readings. In the Apollo 16 mission, dust coated the lunar rover battery mirrors and overheated it.
ESA PILOT
Before the Ukraine invasion, ESA contribution with a optical navigation camera, aka PILOT-D. But this and other ESA cooperation was pulled off.
Planned pre-landind burn: 11:10 UTC Aug 19 , 2023( 14:10 Moscow time)
Crash:
At 09:47 Moscow Time ( 1 min after moonrise in Crimea) on Aug. 20, 2023, Roskosmos announced that the communications with the spacecraft were interrupted at 14:57 Moscow Time on August 19(moon altitude is 35.64 degree in moscow, 46.47 degree in crimea), during the orbit correction. According to the State Corporation, all attempts to communicate with spacecraft attempted on August 19 and 20 failed. The preliminary analysis showed that the spacecraft entered into an unplanned orbit and crashed into the surface of the Moon, the State Corporation said.
It had lost contact with the spacecraft 47 minutes after the start of the engine firing ( so at least Luna 25 has been transmitting during this period)
According to Roskosmos a special inter-agency commission was being formed to investigate the cause of the failure.
The main cause is the engine burned for 127 seconds instead of planned 84 seconds.
23 Aug
Trajectory simulated that the spacecraft fell into the 42-kilometer Pontecoulant G crater in the southern hemisphere 60.1 E 57.2S
31 Aug
Update from LRO: 61.360E 57.865S
about 400 kilometers short of Luna 25’s intended landing point at 69.545 degrees south, 43.544 degrees east.
16 Sep
TASS revealed that accelerometer was not turned on in last moments
But why? Wrong thrust /valve command setting? All the previous TCMs seemed to be spot on. What such simple mistake happened in such final critical phase?
Why didn't Roscosmos abort the engine burn?
Communication blackout?
Luna 25 was well within the communication zone during this de orbit burn, so saying it was in the "blackout zone" is invalid (所謂測控弧段限制).
Moon set was 21:09 moscow time, ie 6 hours after the de-orbit burn
Oct 2023:
The investigation into the failure found that the neither the accelerometer or its back up transmitted the necessary data required to turn off the engine.
Specifically, there was abnormal communication between the on-board control system and the accelerometers integrated in the BIUS-L device (angular velocity measurement unit).
Nominally during this manoeuvre, after the impulse begins, the accelerometers should measure the velocity of the spacecraft and give a signal to the control system when it reaches the programmed parameters. Then, the lander’s control system gives the engines a command to stop working.
However, the control system was overwhelmed with messages from other systems which were given higher priority (Seradata comment: a likely design error) and the accelerometers were not turned on in time to measure the impulse. And so no engine shutdown command could be sent. Seradata
Reference:
track id:
international: 2023-118
Norad: 57600, 57601
Next missions:
From Yuri Borisov of Roscosmos,
Luna 25 by 11 Aug 2023
Luna 26 +4 years
Luna 27 + 5 years
Luna 28 + 7 years
crewed mission + ? Years?
Reference:
SPACEPILOT-D
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