The mission operation to deploy the MINERVA-Ⅱ1 rovers will be conducted from September 19 – 21. On September 19, activities will focus on preparation for the spacecraft to descend towards asteroid Ryugu and on September 20, the actual descent will begin. The scheduled deployment of the MINERVA-Ⅱ1 rovers is on September 21.
The approximate schedule currently planned is shown in the following table. The safety of the spacecraft is a priority in all operations, so the schedule may change depending on the current situation.
MINERVA-Ⅱ1 main schedule for deployment
|Date & Time（UTC）||Date & Time（JST）||Spacecraft speed (cm/s)||HP altitude (m)||Near-point altitude (m)||Event|
|9/19 00:00||9/19 09:00||０||20,000||Communication via Usuda Deep Space Center begins|
|9/19 08:10||9/19 17:10||Communication via Madrid DSN begins|
|9/19 16:00||9/20 01:00||Comm. via Goldstone DSN begins|
|9/20 00:00||9/20 09:00||Comm. via Usuda begins|
|9/20 04:10||9/20 13:10||confirm readiness for descent|
|9/20 05:10||9/20 14:10||-40||20,000||Begin descent|
|9/20 07:10||9/20 16:10||Comm. via Canberra DSN begins|
|9/20 08:10||9/20 17:10||Comm. via Madrid DNS begins|
|9/20 10:00||9/20 19:00||13,000|
|9/20 15:30||9/21 00:30||-10||5,000||Decelerate descent speed ΔV|
|9/20 16:00||9/21 01:00||Comm. via Goldstone DSN begins|
|9/20 18:30||9/21 03:30||4,000|
|9/21 00:00||9/21 09:00||Comm. via Usuda begins|
|9/21 00:00||9/21 09:00||2,000|
|9/21 00:10||9/21 09:10||1,500|
|9/21 03:00||9/21 12:00||500|
|9/21 03:40||9/21 12:40||250|
|+50||~60||Post deployment upward ΔV|
|9/21 05:40||9/21 14:40||TBD||Increase ΔV to return to home position|
|9/21 07:20||9/21 16:20||Comm. via Canberra DSN begins|
|9/21 08:10||9/21 17:10||Comm. via Madrid DSN begins|
|9/21 16:00||9/22 01:00||Comm. via Goldstone DSN begins|
|9/22 00:00||9/22 09:00||Comm. via Usuda begins|
- Time: Approximate schedule time (in 10 -minute 5-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.
- dV, ΔV：acceleration of the spacecraft
- free fall：The speed of the spacecraft is not controlled, but falls due to the pull of Ryugu’s gravity.
- GCP-NAV：Ground Control Point Navigation, tool for image guided navigation during the descent operation.
- HP：home position
- LIDAR：laser altimeter
- ONC-T：Optical Navigation Camera Telescopic (installed on the bottom of the spacecraft).
- ONC-W1：Optical Navigation Camera Wide angle (installed on the bottom of the spacecraft).
- ONC-W2: Optical Navigation Camera Wide angle (installed on the side of the spacecraft).
- Attitude scan：change the attitude of the probe to photograph MINERVA-Ⅱ1
- constant descent velocity： the spacecraft descends at a nearly constant speed. At first, this speed is about 40 cm/s. From an altitude of about 5km, the speed is about 10 cm/s.
- Trigger Altitude：when this altitude is reached, the spacecraft’s speed will be controlled.
- Additional free fall for preventing plume contamination: the spacecraft will not use thrusters during the period shown in the figure when MINERVA-II1 is in free fall. This is to avoid thruster gas hitting MINERVA-II1.