FORTE observations of lightning radio‐frequency signatures: Capabilities and basic results

Abstract

Abstract. The FORTE satellite, launched on August 29, 1997, carries both radiofrequency-receiver and optical (imaging and photometric) payloads for the study of lightning. The radio-frequency (RF) data for the first 7 months of operation are described, both to illustrate the satellite's capabilities and to explain the basic statistical findings so far. FORTE's multichannel RF trigger system represents a significant advance in spacebased monitoring of lightning emissions. We are able to observe even rather weak and diffuse RF emissions from lightning and are no longer limited to the brightest known events, "transionospheric pulse pairs," or TIPPs. We do see TIPPs, and we show that the FORTE observations of TIPPs are consistent only with the second pulse's being due to a ground reflection. We find that TIPPs are basically bimodal in character, one type having a steep roll-off of power from 38 to 130 MHz and the other being essentially flat-spectrum in that range. The steep-spectrum TIPPs cluster together in the manner of most RF emissions from lightning, while the flat-spectrum events tend to maintain a wider spacing (>0.1 s) between recurrent emissions. The FORTE Satellite and RF PayloadWe provide here only a sketch of FORTE's RF capabilities. A longer discussion will be given in a separate engineering paper.FORTE was launched on August 29, 1997, into a 70 ø inclination orbit, nearly circular at 800 km altitude. Data acquisition commenced within days and has continued without serious interruption through the writing of this paper (April 1998). The FORTE satellite contains both a suite of RF receivers and the Optical Lightning System (comprising a charge-coupled device (CCD) imager and a fast broadband photometer). This paper will introduce the performance and capabilities of the RF payload [Enemark and Shipley, 1994] as reflected in RF data gathered 337

Joint radio and optical observations of the most radio-powerful intracloud lightning discharges

“…This study uses data from instruments aboard the FORTE satellite, launched in August 1997 into a circular orbit (altitude ∼ 825 km) with 70-degree inclination (Jacobson et al, 1999). The satellite carried four principal scientific instruments and had ample on-board memory.…”

“…One of these satellites was Alexis Massey and Holden, 1995;Massey et al, 1998), launched in 1993, while the other was Fast On-orbit Recording of Transient Events, or FORTE (Jacobson et al, 1999), launched in 1997. FORTE also carried optical payloads for lightning studies Suszcynsky et al, 2000Suszcynsky et al, , 2001.…”

Revisiting "Narrow Bipolar Event" intracloud lightning using the FORTE satellite

“…This is because an emitted impulse of VHF has two paths to the satellite, the first being direct, and the second being downward to the reflective ground and thence (via reflection) up to the satellite Jacobson et al, 1999Jacobson et al, , 2011Massey and Holden, 1995;Massey et al, 1998a). The delayed arrival of the reflected pulse, with respect to the first, gives the impression of a "pulse pair".…”

An overview of the lightning and atmospheric electricity observations collected in southern France during the HYdrological cycle in Mediterranean EXperiment (HyMeX), Special Observation Period 1

“…They usually operate at specific wavelength ranges and are sensitive to some components of the lightning discharges. For instance, some groundbased or space-borne sensors detect electromagnetic radiation emitted in the very high frequency (VHF) domain (e.g., Proctor, 1981;Shao and Krehbiel, 1996;Jacobson et al, 1999;Krehbiel et al, 2000;Defer et al, 2001;Defer and Laroche, 2009). Other instruments detect the radiation emitted by lightning flashes in the optical wavelength (e.g., Light et al, 2001;Christian et al, 2003) or in the very low frequency / low frequency (VLF / LF) range (e.g., Cummins et al, 1998;Smith et al, 2002;Betz et al, 2008Betz et al, , 2009.…”