QZSS Constellation Status Information



Satellites

The Quasi-Zenith Satellite System (QZSS) currently comprises a single satellite in an inclined geo-synchronous orbit.
Common Name SVN Int. Sat. ID NORAD ID PRN Notes
QZS-1 (Michibiki) J001 2010-045A 37158 J01  


Spacecraft Characteristics

A comprehensive collection of technical information with associated references for the QZSS spacecraft can be obtained at ESA's eoPortal . Physical key parameters of the spacecraft are summarized below:

Parameter QZS-1
Launch mass 4100 kg
Dry mass 1800 kg
Body size 2.9 m x 3.1 m x 6.2 m
Solar array size n/a
Span width 25.3 m
Cross section n/a
SRP acceleration 156 nm/s2

The QZS-1 spacecraft is equipped with a primary L-band antenna (L-ANT) for transmission of the L1 C/A, L1C, L2C, L5, and L6 LEX signals, whereas a separate (LS-ANT) antenna is used for the L1 SAIF signal. In addition, a laser retroreflector array (LRA) is provided to enable precise distance measurements using satellite laser ranging.


Fig. 1 QZSS spacecraft reference system and sensor location (JAXA)

Phase center coordinates of the GNSS antennas and the LRA as recommended for QZS-1 processing within the MGEX project are provided in the following table. All values refer to the spacecraft coordinate system illustrated in Fig. 1. The spacecraft coordinate system is aligned with the main body axes and originates near the center of the launch adapter plane:
  • the +zs/c-axis is oriented along the boresight direction of the L-ANT antenna;
  • the +ys/c-axis is parallel to the rotation axis of the solar panels and oriented such that the LS-ANT is located in the first quadrant relative to the L-ANT;
  • the +xs/c-axis completes a right handed system;
While the center of mass (CoM) may shift by roughly 3 cm over the mission life-time, the value for mid 2012 is adopted as a conventional value for a harmonized processing. Begin-of-life (BoL) and End-of-life (EoL) values are given for information, only. CoM coordinates previously reported in [2] for satellite laser ranging support are superseded by more recent values provided in [1].

QZS-1
  Coordinates (w.r.t. origin) Coordinates (w.r.t. CoM) Reference
xs/c ys/c zs/c xs/c ys/c zs/c
L-ANT L1 0.0 mm 0.0 mm +5017.8 mm +0.9 mm -2.9 mm +3197.9 mm [1]
L-ANT L2 0.0 mm 0.0 mm +4812.8 mm +0.9 mm -2.9 mm +2992.9 mm [1]
L-ANT L5 0.0 mm 0.0 mm +4897.8 mm +0.9 mm -2.9 mm +3077.9 mm [1]
L-ANT L6 0.0 mm 0.0 mm +4967.8 mm +0.9 mm -2.9 mm +3147.9 mm [1]
LS-ANT L1 +1150.0 mm +700.0 mm +4835.0 mm +1150.9 mm +697.1 mm +3015.1 mm [1]
LRA   -1150.0 mm -550.0 mm +4505.3 mm -1149.1 mm -552.9 mm +2685.4 mm [2]
CoM (BoL)   -0.9 mm +2.9 mm +1819.2 mm       [1]
CoM (Jul 2012)   -0.9 mm +2.9 mm +1819.9 mm       [1]
CoM (EoL)   -0.9 mm +3.1 mm +1851.2 mm       [1]


Other than for GPS and GLONASS, the attitude law that describes the orientation of the QZSS satellites in space, depends on the elevation of the Sun relative to the orbital plane (also known as β angle):
  • For |β|>20° the satellite is operated in "yaw-steering mode" (Fig. 2). Here, the +zs/c-axis is pointed to the Earth, while the ys/c-axis is oriented perpendicular to the plane made up by the Sun, Earth, and satellite. Furthermore, the +xs/c-axis is pointed to "deep space" (i.e. away from the Sun) at all times to minimize heating of the onboard clocks. The yaw-steering mode resembles the standard attitude law of the GPS satellites as employed in IGS processing standards but differs in the sign of the x-axis (GPS: Sun in +xIGS hemisphere; QZSS: Sun in -xs/c hemisphere).
  • For |β|<20° the satellite is operated in "orbit normal mode". While the +zs/c-axis is again pointed towards the center of the Earth, the +ys/c-axis is held perpendicular to the orbital plane and anti-parallel to the orbital angular momentum vector.
While the location of the L-ANT phase center relative to the center of mass is essentially independent of the yaw-angle (i.e. the rotation about the +zs/c-axis), knowledge of the actual attitude is required for phase wind-up modeling and for the computation of the absolute LS-ANT and LRA positions.


Fig. 2 QZSS attitude modes (from [3])

References

[1] S. Kogure, priv. comm. (20 July 2012)
[2] QZS-1 ILRS SLR Mission Support Request Form - Retroreflector Information
[3] Y. Ishijima, N. Inaba, A. Matsumoto, K. Terada, H. Yonechi, H. Ebisutani, S. Ukawa, T. Okamoto, "Design and Development of the First Quasi-Zenith Satellite Attitude and Orbit Control System", Proceedings of the IEEE Aerospace Conference, March 7-14 2009, Big Sky, MT, USA, (2009). DOI 10.1109/AERO.2009.4839537


Events

Date UTC Satellite PRN Description Notes
~2010/12/15   QZS-1 J001 Transmission of standard codes Kishimoto et al. (2012)
2011/02/16 07:00 QZS-1 J001 Transition to orbit normal mode Hauschild (2011); CONGO monitoring
2011/02/16   QZS-1 J001 Orbit maneuver Hauschild (2011); TUM/CONGO
2011/02/16 17:30 QZS-1 J001 Return to yaw steering mode Hauschild (2011); CONGO
2011/03/07 10:00 QZS-1 J001 Transition to orbit normal mode
2011/04/20 08:13 QZS-1 J001 Return to yaw-steering mode
2011/05/22   QZS-1 J001 L1-C/A and L2C signals set healthy Kishimoto et al. (2012)
2011/07/14   QZS-1 J001 L1C and L5 signals set healthy Kishimoto et al. (2012)
2011/07/16 01:30 QZS-1 J001 Start of RESSOX NAQU 2011002
2011/07/23 08:10 QZS-1 J001 End of RESSOX NAQU 2011004
2011/09/07 09:20 QZS-1 J001 Transition to orbit normal mode
2011/10/22 08:05 QZS-1 J001 Return to yaw-steering mode
2012/01/04 09:21 QZS-1 J001 Unusable (until 21:19 UTC) NAQU 2012001-002
2012/01/21 01:28 QZS-1 J001 Start of RESSOX NAQU 2012003-005
2012/01/28 06:55 QZS-1 J001 End of RESSOX NAQU 2012003-005
2012/02/24 11:04 QZS-1 J001 Unusable (until 12:40 UTC) NAQU 2012006-007
2012/03/03 09:55 QZS-1 J001 Transition to orbit normal mode
2012/03/07 05:35 QZS-1 J001 Unusable (until 16:18 UTC) NAQU 2012008-009
2012/04/16 08:12 QZS-1 J001 Return to yaw-steering mode
2012/05/02 01:32 QZS-1 J001 Unusable (until 2012/05/03 01:13 UTC) NAQU 2012010-011
2012/06/03 16:42 QZS-1 J001 Unusable (until 2012/06/04 01:15 UTC) NAQU 2012013-014
2012/07/04 21:30 QZS-1 J001 Unusable (until 2012/07/05 12:11 UTC); switched from Rb clock 2 to Rb clock 1 NAQU 2120015-016
2012/09/03 09:21 QZS-1 J001 Transition to orbit normal mode
2012/09/29 14:07 QZS-1 J001 Unusable (until 2012/09/29 18:25 UTC) NAQU 2012017-018
2012/10/18 08:07 QZS-1 J001 Return to yaw-steering mode
2012/11/07 12:56 QZS-1 J001 Unusable (until 2012/11/08 21:24 UTC) NAQU 2012019-020
2012/11/07 QZS-1 J001 Orbit Maneuver
2012/12/05 21:21 QZS-1 J001 Unusable(until 2012/12/06 02:05 UTC) NAQU 2012021-022
2013/01/30 06:25 QZS-1 J001 Unusable(until 2013/01/30 08:35 UTC) NAQU 2013001-002
2013/02/27 09:55 QZS-1 J001 Transition to orbit normal mode
2013/04/13 08:18 QZS-1 J001 Return to yaw-steering mode
2013/05/01 01:14 QZS-1 J001 Unusable (until 2013/05/02 00:16 UTC) NAQU 2013003-004
2013/05/01 QZS-1 J001 Orbit Maneuver
2013/08/30 09:27 QZS-1 J001 Transition to orbit normal mode
2013/10/30 12:15 QZS-1 J001 Unusable (until 2013/10/31 13:24 UTC) NAQU 2013005-006
2013/11/11 19:56 QZS-1 J001 Unusable (until 2013/11/11 23:30 UTC) NAQU 2013007-008


Notes:
  • Complementary information on the current status of QZSS is provided at the QZ-Vision web site. This site also provides the QZSS Interface Specification and Notice Advisory to QZSS Users (NAQU) messages.
  • Supplementary information related to Michibiki operations can also be found at the QZSS project web site.
  • QZSS employs distinct PRNs for the L1 SAIF SBAS signal (PRN(SAIF) = 183, 184, ...) and the other ranging signals (PRN(std) = 193, 194,...). In order to ensure a unique RINEX satellite number for each QZSS satellite, it is recommended to consistently use the satellite number "Jnn" with n = PRN(std)-193=PRN(SAIF)-183. Use of an SBAS RINEX satellite number "Snn" with nn = PRN(SAIF)-100 is deprecated.
  • The experimental remote synchronization system for an onboard crystal oscillator (RESSOX) of QZSS aims at the use of a ground-controlled low cost oscillator onboard a GNSS satellite as an alternative to a high-performance atomic frequency standard.

Last Updated: 2013/10/31