We report the performance of the 13.7-meter Taeduk Radio Astronomy Observatory (TRAO) radio telescope. The telescope has been equipped with a new receiver, SEQUOIA-TRAO, a new backend system, FFT2G, and a new VxWorks operating system. The receiver system features a 16-pixel focal plane array using high-performance MMIC preamplifiers; it shows very low system noise levels, with system noise temperatures from 150 K to 450 K at frequencies from 86 to 115 GHz. With the new backend system, we can simultaneously obtain 32 spectra, each with a velocity coverage of 163 km s−1 and a resolution of 0.04 km s−1 at 115 GHz. The new operating system, VxWorks, has successfully handled the LMTMC-TRAO observing software. The main observing method is the on-the-fly (OTF) mapping mode; a position-switching mode is available for small-area observations. Remote observing is provided. The antenna surface has been newly adjusted using digital photogrammetry, achieving a rms surface accuracy better than 130 µm. The pointing uncertainty is found to be less than 5'' over the entire sky. We tested the new receiver system with multi-frequency observations in OTF mode. The aperture efficiencies are 43±1%, 42±1%, 37±1%, and 33±1%, the beam efficiencies are 45±2%, 48±2%, 46±2%, and 41±2% at 86, 98, 110, and 115 GHz, respectively.

Abstract
1. INTRODUCTION
2. UPGRADED TELESCOPE SYSTEMS
    2.1. Telescope
    2.2. Receiver
    2.3. Backend
    2.4. Operating System and Data Reduction
3. TELESCOPE BEAM SIZES AND EFFICIENCIES
4. SPECTRAL LINE OBSERVATIONS
5. SUMMARY
ACKNOWLEDGMENTS
REFERENCES

• Chang Won Lee(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea)
• Youngung Lee(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea)
• Sung-Ju Kang(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea)
• Do-Heung Je(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea)
• Do-Young Byun(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea/University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea)
• Changhoon Lee(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea)
• Jaehoon Jung(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea)
• Hyunwoo Kang(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea)
• Il-Gyo Jeong(Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Daejeon, Korea/SETsystem, Inc., 4th Floor Hongnam BD, 16-3, Gangnam-daero 8-gil, Seocho-gu, Seoul, Korea)