Intro
Accurate Ranging system for Geodetic Observation (ARGO)
ARGO
- Korean SLR project
- Accurate ranging system for geodetic observation
Development Period
- 2008–2016 (nine years)
Final Goal
- One mobile system (40 cm/10 cm): ARGO-M (2008–2013)
- One fixed system (100 cm): ARGO-F (2013–2016)
Objectives
- Space geodesy research and Global Earth Observation System of Systems/Global Geodetic Observing System (GEOSS/GGOS) contribution by laser ranging for satellites with Laser Retroreflector Array
- Precise orbit determination through laser ranging measurement with millimeter-level accuracy
- Contribution to international SLR societies and International Laser Ranging Service (ILRS) network participation
History
Development
- 2004-12 – 2005-11 Research on foundational techniques
- 2005-07–2006-06 STRM planning research
- 2007 National R&D agreement with Ministry of Science and Technology
- 2008 Start of ARGO-M SLR system development
ARGO-M
- 2008–2012 ARGO-M (movable SLR system) development
- 2012-09-26 First shot
- 2012-11-02 Became a member of ILRS (observatory: DAEK)
- 2013-10-22 Observation data uploaded to ILRS
- 2014-04-11 Certification as ILRS active station
- 2015-04 ARGO-M Seojong-Si move & observatory dedication ceremony
ARGO-F
- 2013-07 KASI-Geochang-Gun memorandum of understanding
- 2013-12 High-speed TMS design (research commissioned)
- 2013-08 Purchase of observatory site (4,950 m2)
- 2014-06 International joint development contract with EOS in Australia
- 2014-11 Observatory groundbreaking ceremony
- 2015-10 Completion of observatory construction
- 2016-04 Observatory dedication ceremony
Facilities
ARGO-M is designed to enable 2-kHz laser ranging for both daytime and nighttime tracking of satellites at altitudes between 300 and 25,000 km. It has a bistatic optical path employing 40-cm receiving and 10-cm transmitting telescopes. For daylight tracking and 2-kHz laser ranging, ARGO-M adopts an event timer, a special narrow-band-pass filter, and a high-energy laser with 2.5 mJ of energy per pulse at 2 kHz. Fig. 1 shows the appearance of the ARGO-M at the headquarters of KASI, and Fig. 2 shows the firing of the laser from ARGO-M.
Figure 1. Appearance of ARGO-M
Figure 2. Laser Tracking in ARGO-M
Figure3. Configuration of ARGO-M
| Item | Parameter | Description/value |
|---|---|---|
| Telescope | Optical path | Bistatic |
| Rx/Tx telescopes | 40/10 cm | |
| Primary mirror F-ratio | 1.5 | |
| Transmit beam divergence | 5–200 arcsec | |
| Max slew rate and acceleration | 20 deg/s (AZ), 10 deg/s (EL); >5 deg/s2 (AZ), >2 deg/s2 (EL) |
|
| Tracking & pointing accuracy | <5 arcsec | |
| Detector | Type | C-SPAD |
| Quantum efficiency | 20% | |
| Primary mirror F-ratio | 100 ps to 2 ns | |
| Laser | Wavelength | 532 nm |
| Pulse energy or power | 2.5 mJ @ 2 kHz | |
| Pulse width | 50 ps | |
| Repetition rate of operation | 2 kHz | |
| Beam diameter @ Tx telescope | 7.5 cm | |
| Timing system | Type | Event timer |
| Single-shot RMS resolution | 3.5–4 ps | |
| Aircraft detection | Type | Radar |
| Max. detection range | 40 km |
Table 1. Major specifications of ARGO-M
ARGO-F (Fixed), Gamak Station
Figure 4. ARGO-F design
Telescope
The ARGO-F telescope was designed as a confocal paraboloid beam expander (Mersenne) configuration with a primary mirror having a focal ratio of f/1.5 and a Coude path. It can point accurately to an object in the sky to 1 arcsec and can track at 30 degrees per second (AZ) and 20° degrees per second (EL) within 1 arcsec accuracy. It is a common Coude type having the same transmit and receive paths. Its optical tube assembly will be manufactured by EOS Space Systems in Australia, and its tracking mount will be manufactured by Justek in the Republic of Korea.
Laser
The ARGO-F will have two lasers, for laser ranging and for space debris laser ranging. The first is a Nd:YAG crystal solid-state laser with a wavelength of 532 nm. Its pulse width is less than 20 ps, and its repetition rate is 60 Hz. Each pulse has a nominal energy of 15 mJ. The second laser is a high-energy laser with a wavelength of 532 nm that is manufactured by EKSPLA. Each pulse has an energy of less than 2500 mJ. Its pulse width is 4–6 ns, and the repetition rate is 10 Hz.
| Type | Nd:YAG |
|---|---|
| Wavelength | 532 nm |
| Pulse width | ≤20 ps |
| Primary mirror F-ratio | 1.5 |
| Repetition rate | 60 Hz nominal (can support collision band avoidance) |
| Pulse energy @ 532 nm | 15 mJ nominal, 20 mJ maximum (average power ≥1 W) |
| Beam quality | M2 ≤ 1.35 |
Table 2. Major specifications of ARGO-F
| Type | Site |
|---|---|
| Wavelength | 532 nm |
| Pulse width | ≤4–6 ns |
| Repetition rate | 10 Hz |
| Pulse energy @ 532 nm | 2500 mJ (average power ~25 W) |
Table 3. Major specifications of DLT
Transmitting/Receiving (Tx/Rx) Optical System
The Tx/Rx system consists of a T/R disk mirror, C-SPAD, spatial filter, spectral filter, and neutral density filter. The main purpose of the Tx/Rx system is to switch between the transmitting laser and reflected receiving laser using the T/R disk mirror and to detect the laser signal reflected by a satellite. The T/R disk mirror has two through-holes synchronized to the laser firing and is rotated at 30 Hz for a 60 Hz laser repetition rate.
Representative Result
Sejong SLR system joined ILRS network
- Registration Date: 2015-08-07
- Code and Monument Number – Sejong (SEJL), 7394
- DOMES Numbers: 23942601
10kHz ARGO Range Gate Generator and Operating System Development
- Existing 2-kHz repetition laser tracking stations: fewer than about 10 ILRS stations
- KASI 10-kHz laser tracking system: the first developed in the world (2015-05)
- ARGO-M performance upgrade: 2 kHz → 5 kHz (owing to the installed laser specifications)
ARGG : ARGO Range Gate Generator
10kHz ARGO Range Gate Generator Test Block Diagram
SLR Raw Data of Stella
SLR Data Processing Result of Stella