Transient Attitude Motion of TNS-0#2 Nanosatellite during Atmosphere Re-Entry

Round 1

Reviewer 1 Report

The paper presents the attitude motion reconstruction of the TN S-0 #2 nannosatellite during the last months of its mission. The passive satellite attitude control system uses a  permanent magnet with hysteresis rods. The satellite attitude was determined based on  the post-flight measurements processessing using the data provided by a three-axis magnetometer and a set of Sun sensors. Among the contributions of the paper I mention: determination of the initial condition for the state propagator, estimation of the constant bias in the magnetometer measurements, reconstruction of the angular velocity components, magnetic stabilization, transient attitude motion and aerodynamic stabilization analysis.

The paper is well organised and clearly written.

The conclusions are consistent with the presented results and the bibliography includes relevant papers.

I recommend the paper for publication. 

Author Response

Thank you for the paper evaluation, we highly value it!

Reviewer 2 Report

The manuscript reports the attitude control performance at different stages of TNS-0 #2 satellite, which is quite informative to the related researchers. A few questions and recommendation from my side are listed below:

Line52-53: This is due to the extremely short time between the dense upper atmospheric layers en-tering and the satellite operation termination due to the heating.

Do you mean the satellite normally stop operation during this transition stage? From your study, the satellite exhibited the tumbling transient motion for about two weeks and the attitude cannot be maintained during this period. Does it mean the data from most nano-satellite of the transition are generally useless?

Fig. 6 gives the predicted angular velocity, how about the measured angular velocity from the sensors (e.g., GPS/GLONASS receiver)?

Why the sensor numbers of the model and measurement are not correspondent (1 2 3 4 5 for model, 1 2 3 5 6 for measurement)?

The readers cannot tell the difference of figure 9 and 11 from the figure name. Please give detailed description of the figure in the title, e.g., Deviation ……on Oct 2.

The general English language of the manuscript should better be improved. To name a few: the sentence in line 228-229, line 106-107 (à sensors' measurement processing technique of TNS-0 #2 is presented? ), equations in Section3 not displayed properly.

Author Response

The authors are very grateful for the efforts on reviewing the paper. We addressed all the questions and the suggestions. The answers are placed right after the reviewer comments highlighted in italics.

1) The manuscript reports the attitude control performance at different stages of TNS-0 #2 satellite, which is quite informative to the related researchers. A few questions and recommendation from my side are listed below:

Line52-53: This is due to the extremely short time between the dense upper atmospheric layers en-tering and the satellite operation termination due to the heating.

Do you mean the satellite normally stop operation during this transition stage? From your study, the satellite exhibited the tumbling transient motion for about two weeks and the attitude cannot be maintained during this period. Does it mean the data from most nano-satellite of the transition are generally useless?

The data from the nanosatellites during the transient motion is not entirely useless. Some payloads operate even with high tumbling rate. The data from the attitude sensors is useful for the attitude motion reconstruction as we did in the paper. The main problem that the telemetry for most of the satellites with passive attitude control is unavailable.

Actually, we cannot say definitely what is normally happening with the satellites during the last two weeks during the transient motion from magnetic to aerodynamic stabilization. We can only judge from the literature that we cannot find the relevant works on transient stage. Probably, some of the satellites with passive stabilization were still functional during re-entry and even some telemetry was available (though standard radio link encounters a problem with tracking satellite by on-ground antenna, since the orbit evolves rapidly). However, for some reason it was not published for any of the satellites for the best of authors knowledge. 

2) Fig. 6 gives the predicted angular velocity, how about the measured angular velocity from the sensors (e.g., GPS/GLONASS receiver)?

Unfortunately, TNS-0#2 was not equipped with angular velocity sensor. So, the measured angular velocity is not available. GPS/GLONASS receiver cannot provide such measurements.

3) Why the sensor numbers of the model and measurement are not correspondent (1 2 3 4 5 for model, 1 2 3 5 6 for measurement)?

In Fig.7 was a typo, we corrected it.

4) The readers cannot tell the difference of figure 9 and 11 from the figure name. Please give detailed description of the figure in the title, e.g., Deviation ……on Oct 2.

We added in Fig.11 capture “for 210 days starting from February 1, 2018”.

5) The general English language of the manuscript should better be improved. To name a few: the sentence in line 228-229, line 106-107 (à sensors' measurement processing technique of TNS-0 #2 is presented? ), equations in Section3 not displayed properly.

We improved the English in the paper. We have checked the equations in Section 3, probably there was a problem with word-to-pdf transition.