射电天文研究室知识库

脉冲星观测研究一直是新疆天文台的主要研究方向,未来建设的新疆110 m口径全可动射电望远镜(简称QTT)也将其作为主要研究方向之一。南山25 m射电望远镜当前使用的脉冲星单脉冲观测终端AFB已使用近20年,系统老化严重,为升级现有单脉冲观测系统,也为QTT的终端设计做预研,基于ROACH2研制了一套脉冲星观测系统。该系统采用氢钟与GPS时间同步以提供秒起始信号,对采样时钟计数并打入数据帧以获取精准时间间隔,两者合成即可获得精确时间信息;采用共享内存缓冲区,使数据在多进程间共享实现并行实时处理。该系统可用于脉冲星单脉冲或到达时间观测,也可用于脉冲星、RRAT或FRB等搜寻。已在南山进行单脉冲、长时间折叠、FRB实时搜寻等观测试验,试验数据表明该终端准确、稳定、可靠,已达到投入观测使用的要求。

Pulsar observation and research is the most important research area in Xinjiang Astronomical Observatory, and that will be the main scientific activity of the Xinjiang 110 meter fully moveable telescope (QTT for short). The pulsar single pulse observation backend used in Nanshan 25 m telescope ―AFB has been worked for almost 20 years. Meanwhile, it’s system performance declines with time. Thus, we decided to develop a new pulsar backend based on ROACH2 board not only for upgrading of current single pulse observation system but also be a pre-research for QTT backends system. Some advanced techniques have been used in this system to get a very high time precision and to accelerate the processing efficiency. We use synchronization of hydrogen clock and GPS time to make an accurate integer time in seconds. Specifically, we count the impulse of sampling clock and pack it to the data frame to get a precision decimal seconds first, and then synthesize both to obtain accurate time information. Finally using shared memory for data sharing between different process to get a real time parallel processing. This backend can be used for single pulse or lower precision timing observation, and also used for searching of pulsar, RRAT or FRB. This system has been already tested on Nanshan 25 m telescope using L band receiver, which includes single pulse, pulsar long time integration and FRB searching observation. Testing results showed that this system works well and has good precision, stability and reliability, which can be implemented for pulsar normal observation in Nanshan 25 m telescope, and also can be used for other telescopes.