The second touchdown rehearsal will be performed from October 14 – 16. The purpose of this rehearsal is to confirm the operation characteristics of the LRF (Laser Range Finder) which performs the altitude measurement at short distances. To test this, the spacecraft will descend to an altitude of about 25m. This will be the lowest altitude reached to date.
The first touchdown rehearsal (TD1-R1) was conducted between September 10 – 12. During this operation, problems occurred with the distance measurement taken with the LIDAR (laser altimeter) once the spacecraft had descended to about 600m. This caused the spacecraft to rise autonomously. The issue was addressed by adjusting the settings on the laser altimeter and it was confirmed that there were no further issues during the subsequent separation operations of MINERVA-II1 and MASCOT. As the spacecraft was only able to descend to an altitude of 600m during TD-R1, the LRF characteristics could not be verified. Therefore, we are performing this check with this rehearsal.
Although this is the second time a rehearsal operation has been performed, the name is TD1-R1-A as it is re-starting the challenge of TD1-R1.
Main schedule for the TD1-R1-A operation
| Date & Time（UTC） | Date & Time（JST） | Spacecraft speed (cm/s) | HP altitude (m) | Near-point altitude (m) | Event |
|---|---|---|---|---|---|
| 10/13 23:00 | 10/14 08:00 | ０ | 20,000 | Communication via Usuda Deep Space Center begins | |
| 10/14 08:20 | 10/14 17:20 | Communication via Madrid DSN begins | |||
| 10/14 14:50 | 10/14 23:50 | -40 | 20,000 | Begin descent | |
| 10/14 16:10 | 10/15 01:10 | Comm. via Goldstone DSN begins | |||
| 10/14 19:40 | 10/15 04:40 | 13,000 | |||
| 10/14 23:00 | 10/15 08:00 | Comm, via Usuda begins | |||
| 10/15 01:10 | 10/15 10:10 | -10 | 5,000 | Decelerate descent speedΔV | |
| 10/15 05:00 | 10/15 14:00 | Comm. via Canberra begins | |||
| 10/15 08:50 | 10/15 17:50 | Comm. via Madrid begins | |||
| 10/15 09:50 | 10/15 18:50 | 1,500 | |||
| 10/15 11:50 | 10/15 20:50 | 800 | |||
| 10/15 12:40 | 10/15 21:40 | 500 | |||
| 10/15 13:50 | 10/15 22:50 | 72 | ~25 | ascent ΔV | |
| 10/15 14:10 | 10/15 23:10 | 1,000 | |||
| 10/15 16:00 | 10/16 01:00 | TBD | 6,000 | Increase ΔV to return to home position | |
| 10/15 17:00 | 10/16 02:00 | Comm. via Goldstone begins |
- Time: Approximate schedule time (in 10 minute increments). There is a possibility that this may change during operation. The time is the onboard time, so confirmation of the event is the radiowave propagation time of about 18 minutes later.
- Spacecraft speed: This is the speed relative to the asteroid (minus is towards the asteroid, positive is away). Numerical value is displayed only when speed control is performed. After a speed control operation, the speed changes due to the gravitational force of Ryugu and other celestial bodies.
- HP altitude: Distance to the center of Ryugu.
- Near point altitude: Distance to the surface of Ryugu.
Schematic of the TD1-R1-A operation
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[Enlargement]
Figure 1: Schematic of the TD1-R1-A operation
Hayabusa2 project
2018.10.14